The Securities and Exchange Commission has not necessarily reviewed the information in this filing and has not determined if it is accurate and complete.
The reader should not assume that the information is accurate and complete.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 13F

FORM 13F INFORMATION TABLE
OMB APPROVAL
OMB Number: 3235-0006
Estimated average burden
hours per response: 23.8
COLUMN 1 COLUMN 2 COLUMN 3 COLUMN 4 COLUMN 5 COLUMN 6 COLUMN 7 COLUMN 8
VALUE SHRS OR SH/ PUT/ INVESTMENT OTHER VOTING AUTHORITY
NAME OF ISSUER TITLE OF CLASS CUSIP (x$1000) PRN AMT PRN CALL DISCRETION MANAGER SOLE SHARED NONE
3M CO COM COM 88579Y101 670 3,865 SH   SOLE   3,865 0 0
ABBOTT LABS COM COM 002824100 760 9,041 SH   SOLE   9,041 0 0
ACCENTURE PLC IRELAND SHS CLAS SHS CLASS A G1151C101 212 1,147 SH   SOLE   1,147 0 0
AFLAC INC COM COM 001055102 280 5,101 SH   SOLE   5,101 0 0
ALPHABET INC CAP STK CL A CAP STK CL A 02079K305 2,247 2,075 SH   SOLE   2,075 0 0
ALPHABET INC CAP STK CL C CAP STK CL C 02079K107 812 751 SH   SOLE   751 0 0
AMAZON COM INC COM COM 023135106 2,106 1,112 SH   SOLE   1,112 0 0
AMERICAN EXPRESS CO COM COM 025816109 886 7,181 SH   SOLE   7,181 0 0
AMETEK INC NEW COM COM 031100100 34,698 381,963 SH   SOLE   381,963 0 0
AMPHENOL CORP NEW CL A CL A 032095101 19,757 205,935 SH   SOLE   205,935 0 0
ANHEUSER BUSCH INBEV SA/NV SPO SPONSORED ADR 03524A108 12,599 142,343 SH   SOLE   142,343 0 0
APPLE INC COM COM 037833100 7,066 35,702 SH   SOLE   35,702 0 0
ARCH CAP GROUP LTD ORD ORD G0450A105 25,193 679,425 SH   SOLE   679,425 0 0
BADGER METER INC COM COM 056525108 239 4,000 SH   SOLE   4,000 0 0
BANK AMER CORP COM COM 060505104 408 14,064 SH   SOLE   14,064 0 0
BANK NEW YORK MELLON CORP COM COM 064058100 299 6,762 SH   SOLE   6,762 0 0
BECTON DICKINSON & CO COM COM 075887109 328 1,303 SH   SOLE   1,303 0 0
BERKSHIRE HATHAWAY CLASS B CL B NEW 084670702 19,436 91,177 SH   SOLE   91,177 0 0
BOOKING HLDGS INC COM COM 09857L108 23,640 12,610 SH   SOLE   12,610 0 0
BROWN FORMAN CORP CL B CL B 115637209 372 6,707 SH   SOLE   6,707 0 0
CAMBRIDGE BANCORP COM COM 132152109 1,406 17,246 SH   SOLE   17,246 0 0
CANADIAN PAC RY LTD COM COM 13645T100 26,956 114,590 SH   SOLE   114,590 0 0
CASS INFORMATION SYS INC COM COM 14808P109 1,650 34,041 SH   SOLE   34,041 0 0
CHARTER COMMUNICATIONS INC NEW CL A 16119P108 233 590 SH   SOLE   590 0 0
CHASE CORP COM COM 16150R104 692 6,428 SH   SOLE   6,428 0 0
COLGATE PALMOLIVE CO COM COM 194162103 6,368 88,850 SH   SOLE   88,850 0 0
COMCAST CORP NEW CL A CL A 20030N101 1,610 38,072 SH   SOLE   38,072 0 0
CONOCOPHILLIPS COM COM 20825C104 280 4,598 SH   SOLE   4,598 0 0
COPART INC COM COM 217204106 19,307 258,316 SH   SOLE   258,316 0 0
CSW INDUSTRIALS INC COM COM 126402106 532 7,800 SH   SOLE   7,800 0 0
CTS CORP COM COM 126501105 240 8,714 SH   SOLE   8,714 0 0
DIAGEO P L C SPON ADR NEW SPON ADR NEW 25243Q205 919 5,332 SH   SOLE   5,332 0 0
DIAMOND HILL INVESTMENT GROUP COM NEW 25264R207 718 5,063 SH   SOLE   5,063 0 0
DORMAN PRODUCTS INC COM COM 258278100 19,322 221,735 SH   SOLE   221,735 0 0
DOW INC COM COM 260557103 242 4,905 SH   SOLE   4,905 0 0
DUKE ENERGY CORP NEW COM NEW COM NEW 26441C204 275 3,111 SH   SOLE   3,111 0 0
DUPONT DE NEMOURS INC COM COM 26614N102 352 4,693 SH   SOLE   4,693 0 0
EATON CORP PLC SHS SHS G29183103 413 4,963 SH   SOLE   4,963 0 0
ENSTAR GROUP LIMITED SHS SHS G3075P101 692 3,970 SH   SOLE   3,970 0 0
ENTEGRIS INC COM COM 29362U104 5,169 138,495 SH   SOLE   138,495 0 0
EQUITY COMWLTH COM SH BEN INT COM SH BEN INT 294628102 7,312 224,858 SH   SOLE   224,858 0 0
EXXON MOBIL CORP COM COM 30231G102 402 5,243 SH   SOLE   5,243 0 0
FACEBOOK INC CL A CL A 30303M102 409 2,119 SH   SOLE   2,119 0 0
FRP HLDGS INC COM COM 30292L107 1,536 27,547 SH   SOLE   27,547 0 0
GRACO INC COM COM 384109104 10,938 217,980 SH   SOLE   217,980 0 0
GRAHAM HLDGS CO COM COM 384637104 207 300 SH   SOLE   300 0 0
HEICO CORP NEW CL A CL A 422806208 68,414 661,835 SH   SOLE   661,835 0 0
HEXCEL CORP NEW COM COM 428291108 32,175 397,815 SH   SOLE   397,815 0 0
HINGHAM INSTN SVGS MASS COM COM 433323102 15,407 77,809 SH   SOLE   77,809 0 0
HONEYWELL INTL INC COM COM 438516106 238 1,363 SH   SOLE   1,363 0 0
IAA INC COM COM 449253103 19,194 494,943 SH   SOLE   494,943 0 0
IDEX CORP COM COM 45167R104 24,899 144,641 SH   SOLE   144,641 0 0
ILLINOIS TOOL WKS INC COM COM 452308109 782 5,187 SH   SOLE   5,187 0 0
INGEVITY CORP COM COM 45688C107 1,451 13,801 SH   SOLE   13,801 0 0
INGREDION INC COM COM 457187102 12,838 155,635 SH   SOLE   155,635 0 0
INTEL CORP COM COM 458140100 2,107 44,018 SH   SOLE   44,018 0 0
INTERCONTINENTAL EXCHANGE INC COM 45866F104 25,117 292,260 SH   SOLE   292,260 0 0
INTERNATIONAL BUSINESS MACHS C COM 459200101 699 5,066 SH   SOLE   5,066 0 0
ISHARES GOLD TRUST ISHARES ISHARES 464285105 576 42,700 SH   SOLE   42,700 0 0
JOHNSON & JOHNSON COM COM 478160104 1,926 13,830 SH   SOLE   13,830 0 0
JPMORGAN CHASE & CO COM COM 46625H100 4,979 44,534 SH   SOLE   44,534 0 0
KAR AUCTION SVCS INC COM COM 48238T109 19,411 776,447 SH   SOLE   776,447 0 0
LCI INDS COM COM 50189K103 7,914 87,928 SH   SOLE   87,928 0 0
LEGACY TEX FINL GROUP INC COM COM 52471Y106 25,295 621,340 SH   SOLE   621,340 0 0
LINDE PLC SHS SHS G5494J103 26,665 132,795 SH   SOLE   132,795 0 0
M & T BK CORP COM COM 55261F104 23,131 136,009 SH   SOLE   136,009 0 0
MARTIN MARIETTA MATLS INC COM COM 573284106 380 1,650 SH   SOLE   1,650 0 0
MASTERCARD INC CL A CL A 57636Q104 17,858 67,510 SH   SOLE   67,510 0 0
MCDONALDS CORP COM COM 580135101 591 2,848 SH   SOLE   2,848 0 0
MERCK & CO INC COM COM 58933Y105 1,120 13,360 SH   SOLE   13,360 0 0
MICROSOFT CORP COM COM 594918104 6,951 51,888 SH   SOLE   51,888 0 0
MONDELEZ INTL INC CL A CL A 609207105 502 9,312 SH   SOLE   9,312 0 0
NEWMARKET CORP COM COM 651587107 9,540 23,795 SH   SOLE   23,795 0 0
NIKE INC CL B CL B 654106103 378 4,497 SH   SOLE   4,497 0 0
NORTHERN TR CORP COM COM 665859104 508 5,644 SH   SOLE   5,644 0 0
NOVARTIS A G SPONSORED ADR SPONSORED ADR 66987V109 487 5,333 SH   SOLE   5,333 0 0
NVE CORP COM NEW COM NEW 629445206 861 12,370 SH   SOLE   12,370 0 0
O REILLY AUTOMOTIVE INC NEW CO COM 67103H107 15,413 41,734 SH   SOLE   41,734 0 0
ORACLE CORP COM COM 68389X105 205 3,596 SH   SOLE   3,596 0 0
PAYPAL HLDGS INC COM COM 70450Y103 3,214 28,081 SH   SOLE   28,081 0 0
PEPSICO INC COM COM 713448108 209 1,596 SH   SOLE   1,596 0 0
PERMIAN BASIN RTY TR UNIT BEN UNIT BEN INT 714236106 64 10,500 SH   SOLE   10,500 0 0
PETROLEO BRASILEIRO SA PETROBR SP ADR NON VTG 71654V101 1,280 90,157 SH   SOLE   90,157 0 0
PETROLEO BRASILEIRO SA PETROBR SPONSORED ADR 71654V408 307 19,700 SH   SOLE   19,700 0 0
PFIZER INC COM COM 717081103 563 12,996 SH   SOLE   12,996 0 0
PHILLIPS 66 COM COM 718546104 231 2,474 SH   SOLE   2,474 0 0
PROCTER AND GAMBLE CO COM COM 742718109 201 1,831 SH   SOLE   1,831 0 0
RBC BEARINGS INC COM COM 75524B104 31,295 187,606 SH   SOLE   187,606 0 0
RLI CORP COM COM 749607107 29,131 339,884 SH   SOLE   339,884 0 0
ROPER TECHNOLOGIES INC COM COM 776696106 18,976 51,809 SH   SOLE   51,809 0 0
ROYAL DUTCH SHELL PLC SPONS AD SPONS ADR A 780259206 202 3,100 SH   SOLE   3,100 0 0
SIMPSON MANUFACTURING CO INC C COM 829073105 1,175 17,680 SH   SOLE   17,680 0 0
STARBUCKS CORP COM COM 855244109 1,781 21,243 SH   SOLE   21,243 0 0
TARGA RES CORP COM COM 87612G101 202 5,134 SH   SOLE   5,134 0 0
TD AMERITRADE HLDG CORP COM COM 87236Y108 557 11,156 SH   SOLE   11,156 0 0
TE CONNECTIVITY LTD REG SHS REG SHS H84989104 22,193 231,706 SH   SOLE   231,706 0 0
TELEDYNE TECHNOLOGIES INC COM COM 879360105 23,560 86,025 SH   SOLE   86,025 0 0
TEXAS INSTRS INC COM COM 882508104 2,870 25,010 SH   SOLE   25,010 0 0
TEXAS PAC LD TR SUB CTF PROP I SUB CTF PROP I T 882610108 456 580 SH   SOLE   580 0 0
UNILEVER N V N Y SHS NEW N Y SHS NEW 904784709 516 8,500 SH   SOLE   8,500 0 0
UNILEVER PLC SPON ADR NEW SPON ADR NEW 904767704 425 6,864 SH   SOLE   6,864 0 0
UNION PACIFIC CORP COM COM 907818108 201 1,186 SH   SOLE   1,186 0 0
UNITED TECHNOLOGIES CORP COM COM 913017109 863 6,625 SH   SOLE   6,625 0 0
UNITEDHEALTH GROUP INC COM COM 91324P102 400 1,641 SH   SOLE   1,641 0 0
UTAH MED PRODS INC COM COM 917488108 1,729 18,064 SH   SOLE   18,064 0 0
VISA INC COM CL A COM CL A 92826C839 13,796 79,494 SH   SOLE   79,494 0 0
WELLS FARGO CO NEW COM COM 949746101 406 8,590 SH   SOLE   8,590 0 0
WHITE MTNS INS GROUP LTD COM COM G9618E107 5,572 5,455 SH   SOLE   5,455 0 0
WILLIAMS COS INC DEL COM COM 969457100 315 11,224 SH   SOLE   11,224 0 0
WINMARK CORP COM COM 974250102 5,802 33,510 SH   SOLE   33,510 0 0
ZIX CORP COM COM 98974P100 643 70,694 SH   SOLE   70,694 0 0
ENERGY TRANSFER LP COM UT LTD COM UT LTD PTN 29273V100 170 12,060 SH   SOLE   12,060 0 0
ENLINK MIDSTREAM LLC COM UNIT COM UNIT REP LTD 29336T100 119 11,788 SH   SOLE   11,788 0 0
ENTERPRISE PRODS PARTNERS L P COM 293792107 504 17,450 SH   SOLE   17,450 0 0
MPLX LP COM UNIT REP LTD COM UNIT REP LTD 55336V100 212 6,600 SH   SOLE   6,600 0 0
ONEOK INC NEW COM COM 682680103 336 4,882 SH   SOLE   4,882 0 0
PHILLIPS 66 PARTNERS LP COM UN COM UNIT REP INT 718549207 228 4,612 SH   SOLE   4,612 0 0
DBX ETF TR XTRACK MSCI EURP XTRACK MSCI EURP 233051853 218 7,475 SH   SOLE   7,475 0 0
INVESCO EXCHANGE TRADED FD TR S&P500 EQL WGT 46137V357 13,962 129,514 SH   SOLE   129,514 0 0
ISHARES TR CORE S&P SCP ETF CORE S&P SCP ETF 464287804 1,269 16,211 SH   SOLE   16,211 0 0
ISHARES TR RUS 1000 VAL ETF RUS 1000 VAL ETF 464287598 256 2,011 SH   SOLE   2,011 0 0
ISHARES TR RUS MDCP VAL ETF RUS MDCP VAL ETF 464287473 4,959 55,635 SH   SOLE   55,635 0 0
ISHARES TR SELECT DIVID ETF SELECT DIVID ETF 464287168 18,082 181,619 SH   SOLE   181,619 0 0
SCHWAB STRATEGIC TR INTL EQTY INTL EQTY ETF 808524805 2,561 79,800 SH   SOLE   79,800 0 0
SPDR S&P 500 ETF TR TR UNIT TR UNIT 78462F103 7,230 24,676 SH   SOLE   24,676 0 0
VANGUARD INDEX FDS TOTAL STK M TOTAL STK MKT 922908769 523 3,485 SH   SOLE   3,485 0 0
VANGUARD WHITEHALL FDS INC HIG HIGH DIV YLD 921946406 370 4,235 SH   SOLE   4,235 0 0