VACB 761 is the Vickers Armstrong Castle Bromwich Inspectors identity stamp.
hnx and A3K are correct in saying that the type designation 683 is indeed the Avro Lancaster; however, Castle Bromwich is where they built Spitfires... and the VACB stamp is widely believed to be solely used on Spitfires.
There is however, one major detail overlooked by most people; and that is as follows:
Avro Type 683 – Lancaster Mk. I
S/N Range: HK535-HK579, HK593-HK628, HK644-HK664, HK679-HK710, HK728-HK773 and HK787-HK80
Part of the first production batch ordered from Vickers-Armstrong Limited, Castle Bromwich, on 30-9-41 (originally Mk. II's, changed to Mk. III's on 13-2-43, and ultimately to Mk. I's on 28-4-43), under Contract No. 1336. HK535-HK579, HK593-HK628, HK644-HK664, HK679-HK710, HK728-HK773 and HK787-HK806. Deliveries commenced 12-43; completed 2-45 (average rate of production, slightly less than 4 aircraft per week).
S/N Range:
PP663-PP695, PP713-PP758 and PP772- PP793-PP806, PP820-PP866 and PP880-PP918.
Part of the second production batch of 200 aircraft built by Vickers-Armstrong Ltd., Castle Bromwich, under Contract No. 1336. PP663-PP695, PP713-PP758 and PP772-PP792. Deliveries commenced 2/45; completed 8/45 (average rate of production, approximately 4 aircraft per week).
Of the original order only 99 aircraft were produced, the final 101 aircraft being cancelled: serial numbers PP793-PP806, PP820-PP866 and PP880-PP918.
(Data from
Lancaster-Archive)
Therefore, it is reasonable to assume that the plates indeed came from one of these non-Woodford built Avro Lancasters.