That is certainly odd since AFAIK the letter prefix was continued right up to the end of production at Znaim. The only other four digit no letter guns were the early Polish production, and the first production under the Germans when they started numbering over. The first Z series went to the second A series with no "letterless" numbers between.
But yours has the Znaim wood groved grips, no slot, no takedown lever, probably the large screws without bushings, called Type IIIa by some writers if the bnz pistols are Type IV. (The typing is not consistent and not rigid since changes were phased in and flowed into another with no absolute cutoffs.)
One thing that would help would be a good picture of the serial number. If you want, put a piece of gummed paper over the last number.
By some standards, those are the latest, crudest and least desireable of the Radoms, but some collectors will pay high dollar for the late guns, especially the bnz guns as they are uncommon.