The piece is as mentioned reblued, mostly on chemically entrostet surface, mainly on scabbard and pommel, the blade could have 70/60 % of real blueing, of which partly was probably repaired?, hard to say wout detailed photos, the other parts could be repaired with cold blued, typically flecs on surface.
The switch to letter code in 1940 was mainly done in 1series and it depends on maker offcoarse, Holler is a middle range maker so not extra large the complete Holler/fze production. Even because that code is starting with f letter and was introduced much later as the other earlier letter codes.
i have reported around samples of fze that they could be in range of 7000-10000 pieces, switch around 3xxx d.
