[JV69_BADA]

What is the meaning of "BF274" and "BS428". Is this somethig like a production number?

Forget those 2 test, fully wrong: not represantative of any serial plane:

BS274 IX 3247 R-R M61 FF 12-8-42 R-RH Cv IX M61 incorrectly painted 'BF274' Canadian Pacific retained until scrap. Off CRD contract not to be included in count AAEE 13-8-42 climb and level speed perf and positional error. 6-10-42 range det with 170gal overload tank. Guns removed for cool trials fuel cooler in port wing root 13-10-42 fuel cons trials Boulton Paul 31-10-42 CRD Staverton 11-1-43 AST 18-1-44 major repair mods at Flight Refuelling for fighter towing trials 7-44 58OTU 16-5-45 sold Vickers 11-1-47 Cv Type 509 two-seat trainer RNethAF as H-98 22-3-48

BS428 IX 3298 EA M61 FF 26-8-42 402S 26-8-42 RAE 11-42 neg G trials AAEE 14-1-43 level speed perf with and without 500lb bomb on mod carrier 19-1-43 brief hand trials with 250lb and 500lb bomb comparison trials and range det ice guard and guns removed fuel cool install in wing root. New carrier of RAF design and manufacture install 15-2-43 416S 23-3-43 AST 31-3-43 mods 421S 20-5-43 CAC ops 24-6-43 ros 405ARF 14-9-43 611S 15-10-44 sold scrap H.Bath 24-11-49

i checked what i got and not really much, the best acceptable data is from the spit9 manual, not from WW2spitfireperformance.comstuff, those 2 planes having too much modifications done to be considered as "standard" .