Mapping of Duguid occupation codes to HISCO. Here's a quick take on it:
AG Agriculture.....................HISCO major group 6 - Agricultural, Animal Husbandry And Forestry Workers, Fishermen And Hunters
BT Building Trades.................HISCO minor group 95 - Bricklayers, Carpenters and Other Construction Workers
CM Civil and Municipal.............HISCO minor group 20 - Legislative Officials and Government Administrators
CL Clerical........................HISCO major group 3 - Clerical And Related Workers
DP Domestic and personal services..HISCO major group 5 - Service Workers
EF Engineers, Firemen..............HISCO minor group 98 - Transport Equipment Operators
FR Forestry........................HISCO minor group 63 - Forestry Workers
HF Hunting and fishing.............HISCO minor group 64 - Fishermen, Hunters and Related Workers
LA Labourers.......................HISCO minor group 99 - Labourers Not Elsewhere Classified
MA Manufacturing...................HISCO major groups 7/8/9 - Production And Related Workers
ME Mechanics.......................HISCO major group 8 - Production And Related Workers, Transport Equipment Operators And Labourers
TR Mercantile......................HISCO major group 4 - Sales Workers
MI Mining..........................HISCO minor group 71 - Miners, Quarrymen, Well Drillers and Related Workers
PE Printers, Engravers.............HISCO minor group 92 - Printers and Related Workers
PR Professional....................HISCO major groups 0/1 - Professional, Technical And Related Workers
ST Students........................?
TN Transportation..................HISCO minor group 98 - Transport Equipment Operators
OU Other...........................?
NA Unknown.........................?
UN Not Specified...................?

On this level of granularity, HISCO offers the following:
[0/1] Professional, Technical And Related Workers
[2] Administrative And Managerial Workers
[3] Clerical And Related Workers
[4] Sales Workers
[5] Service Workers
[6] Agricultural, Animal Husbandry And Forestry Workers, Fishermen And Hunters
[7/8/9] Production And Related Workers, Transport Equipment Operators And Labourers

I think the real value of the HISCO coding is at the next level down, though. For each bold heading we have minor groups that we will be able to sort on. So, we can search specifically for jewellers and find people that attested as jeweller, goldsmith, silversmith, whitesmith, etc.

Professional, Technical And Related Workers
[01] Physical Scientists and Related Technicians
[02 or 03] Architects, Engineers and Related Technicians
[04] Aircraft and Ships' Officers
[05] Life Scientists and Related Technicians
[06 or 07] Medical, Dental, Veterinary and Related Workers
[08] Statisticians, Mathematicians, Systems Analysts and Related Technicians
[09] Economists
[11] Accountants
[12] Jurists
[13] Teachers
[14] Workers in Religion
[15] Authors, Journalists and Related Writers
[16] Sculptors, Painters, Photographers and Related Creative Artists
[17] Composers and Performing Artists
[18] Athletes, Sportsmen and Related Workers
[19] Professional, Technical and Related Workers Not Elsewhere Classified

Administrative And Managerial Workers
[20] Legislative Officials and Government Administrators
[21] Managers
[22] Supervisors, Foremen and Inspectors

Clerical And Related Workers
[30] Clerical and Related Workers, Specialisation Unknown
[31] Government Executive Officials
[32] Stenographers, Typists and Card‑ and Tape‑Punching Machine Operators
[33] Bookkeepers, Cashiers and Related Workers
[34] Computing Machine Operators
[36] Transport Conductors
[37] Mail Distribution Clerks
[38] Telephone and Telegraph Operators
[39] Clerical and Related Workers Not Elsewhere Classified

Sales Workers
[41] Working Proprietors (Wholesale and Retail Trade)
[42] Buyers
[43] Technical Salesmen, Commercial Travellers and Manufacturers Agents
[44] Insurance Real Estate, Securities and Business Services Salesmen and Auctioneers
[45] Sales Workers Not Elsewhere Classified

Service Workers
[51] Working Proprietors (Catering, Lodging and Leisure Services)
[53] Cooks, Waiters, Bartenders and Related Workers
[54] Maids and Related Housekeeping Service Workers Not Elsewhere Classified
[55] Building Caretakers, Charworkers, Cleaners and Related Workers
[56] Launderers, Dry-Cleaners and Pressers
[57] Hairdressers, Barbers, Beauticians and Related Workers
[58] Protective Service Workers
[59] Service Workers Not Elsewhere Classified

Agricultural, Animal Husbandry And Forestry Workers, Fishermen And Hunters
[61] Farmers
[62] Agricultural and Animal Husbandry Workers
[63] Forestry Workers
[64] Fishermen, Hunters and Related Workers

Production And Related Workers, Transport Equipment Operators And Labourers
[71] Miners, Quarrymen, Well Drillers and Related Workers
[72] Metal Processors
[73] Wood Preparation Workers and Paper Makers
[74] Chemical Processors and Related Workers
[75] Spinners, Weavers, Knitters, Dyers and Related Workers
[76] Tanners, Fellmongers and Pelt Dressers
[77] Food and Beverage Processors
[78] Tobacco Preparers and Tobacco Product Makers
[79] Tailors, Dressmakers, Sewers, Upholsterers and Related Workers
[80] Shoemakers and Leather Goods Makers
[81] Cabinetmakers and Related Woodworkers
[82] Stone Cutters and Carvers
[83] Blacksmiths, Toolmakers and Machine Tool Operators
[84] Machinery Fitters, Machine Assemblers and Precision-Instrument Makers (except Electrical)
[85] Electrical Fitters and Related Electrical and Electronics Workers
[86] Broadcasting Station and Sound Equipment Operators and Cinema Projectionists
[87] Plumbers, Welders, Sheet Metal and Structural Metal Preparers and Erectors
[88] Jewellery and Precious Metal Workers
[89] Glass Formers, Potters and Related Workers
[90] Rubber and Plastics Product Makers
[91] Paper and Paperboard Products Makers
[92] Printers and Related Workers
[93] Painters
[94] Production and Related Workers Not Elsewhere Classified
[95] Bricklayers, Carpenters and Other Construction Workers
[96] Stationary Engine and Related Equipment Operators
[97] Material Handling and Related Equipment Operators, Dockers and Freight Handlers
[98] Transport Equipment Operators
[99] Labourers Not Elsewhere Classified