Some translated tidbits from Jukka Raunio: "Lentäjän näkökulma II", 1993 (=Pilot's viewpoint II)
Before the US Navy got its F2A-2:s, Brewster company was allowed to deliver 40 F2A-2:s conversions for land bases (carrier equipment was removed) to Belgium, and
they were already designated as version 339B (!!!). Thus the Navy's F2A-2:s were ready only in the end of 1940 and these planes went to USS Saratoga and to USS Lexington in early 1941.
Belgium never got their planes, since they got occupied before the shipments arrived. Instead 6 of them were converted to Finnish versions and the rest were shipped to England, which had ordered 170 F2A-2:s (versions 339E). Most of these were sent to Far-East, where they had little success and got the nickname "Buffalo".
Holland ordered 144 planes, but had the order was cut in half because Brewster could not acquire enough Wright engines. The Dutch planes were designated 339C and 339D. They arrived to Java in Apr 1941 and were fairly successful against Japanese (exchange ratio 2 kills to 1 loss), until their bases were captured.
Last 16 Brewsters (model 339-23 or same as B-439) were delivered to Australia in spring 1942.
Altogether 509 Brewster planes of various versions were built. 55 of them were model B-239 or F2A-1.
F2A-3, which was ordered in Jan 1941, got a longer nose and its empty weight was 2146kg (463kg more than in F2A-1 and 272kg more than in F2A-2).
Finland bought 44 Model 239:s on Dec 16th 1939. Price per plane was 54000 usd plus packaging and delivery costs. In addition 10 spare engines, 20 propellers and other spare parts were bought so that teh total price was 3,4 million usd.
Brewster factory removed all US Navy property from the planes: carrier equipment, weapons, gun sights and gauges. This stripping came as a surprise to Finns, since they had assumed buying complete airplanes.
Finns had to replace all teh missing equipment from elsewhere.. e.g. gauges which were meant for Fokker XXI:s. The planes were assembled in Sweden in spring 1940.
(!!!! I would not consider this a field modification 
!!!)-----
"America's Hundred Thousand" by Francis H. Dean (page 436) mentions almost same manufacturing figures with just minor differences like 20 Aussie Brewsters instead of 16. There is alltogether 33 pages of text, pics, tables and graphs in that boom about F2A (pages 436-469).
