You probably have seen a lot of 93 bolts marked. 1974 was an unusual year for HK. 60s vintage HKs had everything marked with matching numbers. In 1974, HK re-entered the US market with the 41 and 43 but they did not have the same markings. The 1974 41's almost all used 1965 or 66 dated bolt carriers and the other major parts were unmarked. The recievers had numeric dates on them rather than the later date codes. The 43s had HK33 barrels etc. I get the impression this was all rushed/half thought out....
Liaison:Bundeswehr DSO Afghanistan 2002
My 43 is original and also has none of the typical bolt/carrier markings. Looks same as yours.
Recreational HK Collector