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
ABBOTT LABS COM COM 002824100 756 9,041 SH   SOLE   9,041 0 0
ACCENTURE PLC IRELAND SHS CLAS SHS CLASS A G1151C101 221 1,147 SH   SOLE   1,147 0 0
AFLAC INC COM COM 001055102 271 5,178 SH   SOLE   5,178 0 0
ALPHABET INC CAP STK CL A CAP STK CL A 02079K305 2,517 2,061 SH   SOLE   2,061 0 0
ALPHABET INC CAP STK CL C CAP STK CL C 02079K107 962 789 SH   SOLE   789 0 0
AMAZON COM INC COM COM 023135106 1,948 1,122 SH   SOLE   1,122 0 0
AMERICAN EXPRESS CO COM COM 025816109 849 7,181 SH   SOLE   7,181 0 0
AMETEK INC NEW COM COM 031100100 35,684 388,633 SH   SOLE   388,633 0 0
AMPHENOL CORP NEW CL A CL A 032095101 26,677 276,449 SH   SOLE   276,449 0 0
ANHEUSER BUSCH INBEV SA/NV SPO SPONSORED ADR 03524A108 914 9,606 SH   SOLE   9,606 0 0
APPLE INC COM COM 037833100 7,314 32,658 SH   SOLE   32,658 0 0
ARCH CAP GROUP LTD ORD ORD G0450A105 28,333 674,906 SH   SOLE   674,906 0 0
BADGER METER INC COM COM 056525108 215 4,000 SH   SOLE   4,000 0 0
BANK AMER CORP COM COM 060505104 363 12,450 SH   SOLE   12,450 0 0
BANK NEW YORK MELLON CORP COM COM 064058100 306 6,762 SH   SOLE   6,762 0 0
BECTON DICKINSON & CO COM COM 075887109 285 1,125 SH   SOLE   1,125 0 0
BERKSHIRE HATHAWAY CLASS B CL B NEW 084670702 20,077 96,515 SH   SOLE   96,515 0 0
BOOKING HLDGS INC COM COM 09857L108 25,828 13,160 SH   SOLE   13,160 0 0
BROWN FORMAN CORP CL B CL B 115637209 421 6,707 SH   SOLE   6,707 0 0
CAMBRIDGE BANCORP COM COM 132152109 1,294 17,246 SH   SOLE   17,246 0 0
CANADIAN PAC RY LTD COM COM 13645T100 28,396 127,645 SH   SOLE   127,645 0 0
CASS INFORMATION SYS INC COM COM 14808P109 1,838 34,041 SH   SOLE   34,041 0 0
CHARTER COMMUNICATIONS INC NEW CL A 16119P108 243 590 SH   SOLE   590 0 0
CHASE CORP COM COM 16150R104 703 6,428 SH   SOLE   6,428 0 0
COLGATE PALMOLIVE CO COM COM 194162103 6,479 88,135 SH   SOLE   88,135 0 0
COMCAST CORP NEW CL A CL A 20030N101 1,703 37,772 SH   SOLE   37,772 0 0
CONOCOPHILLIPS COM COM 20825C104 268 4,699 SH   SOLE   4,699 0 0
COPART INC COM COM 217204106 20,975 261,116 SH   SOLE   261,116 0 0
CSW INDUSTRIALS INC COM COM 126402106 538 7,800 SH   SOLE   7,800 0 0
CTS CORP COM COM 126501105 475 14,664 SH   SOLE   14,664 0 0
DIAGEO P L C SPON ADR NEW SPON ADR NEW 25243Q205 823 5,032 SH   SOLE   5,032 0 0
DIAMOND HILL INVESTMENT GROUP COM NEW 25264R207 699 5,063 SH   SOLE   5,063 0 0
DORMAN PRODUCTS INC COM COM 258278100 19,137 240,600 SH   SOLE   240,600 0 0
DUPONT DE NEMOURS INC COM COM 26614N102 271 3,794 SH   SOLE   3,794 0 0
EATON CORP PLC SHS SHS G29183103 417 5,019 SH   SOLE   5,019 0 0
ENSTAR GROUP LIMITED SHS SHS G3075P101 533 2,805 SH   SOLE   2,805 0 0
ENTEGRIS INC COM COM 29362U104 6,213 132,015 SH   SOLE   132,015 0 0
EQUITY COMWLTH COM SH BEN INT COM SH BEN INT 294628102 10,339 301,868 SH   SOLE   301,868 0 0
EXXON MOBIL CORP COM COM 30231G102 374 5,293 SH   SOLE   5,293 0 0
FACEBOOK INC CL A CL A 30303M102 370 2,080 SH   SOLE   2,080 0 0
FRP HLDGS INC COM COM 30292L107 1,323 27,547 SH   SOLE   27,547 0 0
GRACO INC COM COM 384109104 14,930 324,285 SH   SOLE   324,285 0 0
HEICO CORP NEW CL A CL A 422806208 65,248 670,515 SH   SOLE   670,515 0 0
HEXCEL CORP NEW COM COM 428291108 32,597 396,890 SH   SOLE   396,890 0 0
HINGHAM INSTN SVGS MASS COM COM 433323102 15,863 83,931 SH   SOLE   83,931 0 0
HOME DEPOT INC COM COM 437076102 202 870 SH   SOLE   870 0 0
HONEYWELL INTL INC COM COM 438516106 231 1,363 SH   SOLE   1,363 0 0
IAA INC COM COM 449253103 20,617 494,048 SH   SOLE   494,048 0 0
IDEX CORP COM COM 45167R104 24,258 148,022 SH   SOLE   148,022 0 0
ILLINOIS TOOL WKS INC COM COM 452308109 813 5,196 SH   SOLE   5,196 0 0
INGEVITY CORP COM COM 45688C107 6,198 73,055 SH   SOLE   73,055 0 0
INGREDION INC COM COM 457187102 13,028 159,378 SH   SOLE   159,378 0 0
INTEL CORP COM COM 458140100 2,109 40,918 SH   SOLE   40,918 0 0
INTERCONTINENTAL EXCHANGE INC COM 45866F104 27,174 294,510 SH   SOLE   294,510 0 0
INTERNATIONAL BUSINESS MACHS C COM 459200101 742 5,103 SH   SOLE   5,103 0 0
ISHARES GOLD TRUST ISHARES ISHARES 464285105 602 42,700 SH   SOLE   42,700 0 0
JOHNSON & JOHNSON COM COM 478160104 1,766 13,649 SH   SOLE   13,649 0 0
JPMORGAN CHASE & CO COM COM 46625H100 3,554 30,194 SH   SOLE   30,194 0 0
KAR AUCTION SVCS INC COM COM 48238T109 21,963 894,634 SH   SOLE   894,634 0 0
LCI INDS COM COM 50189K103 7,881 85,798 SH   SOLE   85,798 0 0
LEGACY TEX FINL GROUP INC COM COM 52471Y106 27,452 630,649 SH   SOLE   630,649 0 0
LINDE PLC SHS SHS G5494J103 27,039 139,580 SH   SOLE   139,580 0 0
M & T BK CORP COM COM 55261F104 26,515 167,849 SH   SOLE   167,849 0 0
MARTIN MARIETTA MATLS INC COM COM 573284106 448 1,634 SH   SOLE   1,634 0 0
MASTERCARD INC CL A CL A 57636Q104 18,569 68,375 SH   SOLE   68,375 0 0
MCDONALDS CORP COM COM 580135101 611 2,848 SH   SOLE   2,848 0 0
MEDTRONIC PLC SHS SHS G5960L103 208 1,918 SH   SOLE   1,918 0 0
MERCK & CO INC COM COM 58933Y105 1,110 13,186 SH   SOLE   13,186 0 0
MICROSOFT CORP COM COM 594918104 5,443 39,149 SH   SOLE   39,149 0 0
MONDELEZ INTL INC CL A CL A 609207105 515 9,312 SH   SOLE   9,312 0 0
NEWMARKET CORP COM COM 651587107 5,993 12,695 SH   SOLE   12,695 0 0
NIKE INC CL B CL B 654106103 414 4,404 SH   SOLE   4,404 0 0
NORTHERN TR CORP COM COM 665859104 564 6,044 SH   SOLE   6,044 0 0
NOVARTIS A G SPONSORED ADR SPONSORED ADR 66987V109 377 4,333 SH   SOLE   4,333 0 0
NVE CORP COM NEW COM NEW 629445206 821 12,370 SH   SOLE   12,370 0 0
O REILLY AUTOMOTIVE INC NEW CO COM 67103H107 17,600 44,164 SH   SOLE   44,164 0 0
ORACLE CORP COM COM 68389X105 203 3,686 SH   SOLE   3,686 0 0
PAYPAL HLDGS INC COM COM 70450Y103 2,914 28,129 SH   SOLE   28,129 0 0
PEPSICO INC COM COM 713448108 240 1,751 SH   SOLE   1,751 0 0
PETROLEO BRASILEIRO SA PETROBR SP ADR NON VTG 71654V101 1,185 90,157 SH   SOLE   90,157 0 0
PETROLEO BRASILEIRO SA PETROBR SPONSORED ADR 71654V408 285 19,700 SH   SOLE   19,700 0 0
PFIZER INC COM COM 717081103 457 12,729 SH   SOLE   12,729 0 0
PHILLIPS 66 COM COM 718546104 253 2,474 SH   SOLE   2,474 0 0
PROCTER & GAMBLE CO COM COM 742718109 228 1,831 SH   SOLE   1,831 0 0
PROGRESSIVE CORP OHIO COM COM 743315103 11,957 154,777 SH   SOLE   154,777 0 0
RBC BEARINGS INC COM COM 75524B104 31,490 189,800 SH   SOLE   189,800 0 0
RLI CORP COM COM 749607107 31,611 340,233 SH   SOLE   340,233 0 0
ROPER TECHNOLOGIES INC COM COM 776696106 18,950 53,141 SH   SOLE   53,141 0 0
SIMPSON MANUFACTURING CO INC C COM 829073105 2,969 42,800 SH   SOLE   42,800 0 0
STARBUCKS CORP COM COM 855244109 1,878 21,243 SH   SOLE   21,243 0 0
TARGA RES CORP COM COM 87612G101 206 5,134 SH   SOLE   5,134 0 0
TD AMERITRADE HLDG CORP COM COM 87236Y108 521 11,156 SH   SOLE   11,156 0 0
TE CONNECTIVITY LTD REG SHS REG SHS H84989104 22,084 236,999 SH   SOLE   236,999 0 0
TELEDYNE TECHNOLOGIES INC COM COM 879360105 27,731 86,125 SH   SOLE   86,125 0 0
TEXAS INSTRS INC COM COM 882508104 3,194 24,710 SH   SOLE   24,710 0 0
TEXAS PAC LD TR SUB CTF PROP I SUB CTF PROP I T 882610108 377 580 SH   SOLE   580 0 0
UNILEVER N V N Y SHS NEW N Y SHS NEW 904784709 510 8,500 SH   SOLE   8,500 0 0
UNILEVER PLC SPON ADR NEW SPON ADR NEW 904767704 465 7,744 SH   SOLE   7,744 0 0
UNITED TECHNOLOGIES CORP COM COM 913017109 870 6,375 SH   SOLE   6,375 0 0
UNITEDHEALTH GROUP INC COM COM 91324P102 365 1,681 SH   SOLE   1,681 0 0
UTAH MED PRODS INC COM COM 917488108 1,731 18,064 SH   SOLE   18,064 0 0
VISA INC COM CL A COM CL A 92826C839 13,539 78,711 SH   SOLE   78,711 0 0
WELLS FARGO CO NEW COM COM 949746101 403 7,990 SH   SOLE   7,990 0 0
WILLIAMS COS INC DEL COM COM 969457100 278 11,545 SH   SOLE   11,545 0 0
WINMARK CORP COM COM 974250102 6,572 37,256 SH   SOLE   37,256 0 0
ZIX CORP COM COM 98974P100 512 70,694 SH   SOLE   70,694 0 0
ENERGY TRANSFER LP COM UT LTD COM UT LTD PTN 29273V100 186 14,210 SH   SOLE   14,210 0 0
ENTERPRISE PRODS PARTNERS L P COM 293792107 499 17,450 SH   SOLE   17,450 0 0
ONEOK INC NEW COM COM 682680103 360 4,882 SH   SOLE   4,882 0 0
PHILLIPS 66 PARTNERS LP COM UN COM UNIT REP INT 718549207 261 4,612 SH   SOLE   4,612 0 0
INVESCO EXCHANGE TRADED FD TR S&P500 EQL WGT 46137V357 12,724 117,727 SH   SOLE   117,727 0 0
ISHARES TR CORE S&P SCP ETF CORE S&P SCP ETF 464287804 406 5,213 SH   SOLE   5,213 0 0
ISHARES TR RUS MDCP VAL ETF RUS MDCP VAL ETF 464287473 1,206 13,440 SH   SOLE   13,440 0 0
ISHARES TR SELECT DIVID ETF SELECT DIVID ETF 464287168 16,667 163,479 SH   SOLE   163,479 0 0
SCHWAB STRATEGIC TR INTL EQTY INTL EQTY ETF 808524805 2,542 79,800 SH   SOLE   79,800 0 0
SPDR S&P 500 ETF TR TR UNIT TR UNIT 78462F103 5,811 19,581 SH   SOLE   19,581 0 0
VANGUARD INDEX FDS TOTAL STK M TOTAL STK MKT 922908769 526 3,485 SH   SOLE   3,485 0 0
VANGUARD WHITEHALL FDS INC HIG HIGH DIV YLD 921946406 256 2,890 SH   SOLE   2,890 0 0