[Ron Wood]

Jerry,
I was aware that Erfurt an Krieghoff ejectors are inspector marked. Probably in the grand scheme of things, such a small mark does not weaken the ejector appreciably. An inspector's mark could be applied during part production. Most likely it was done before hardening as you surmised. However, to add a serial number once the ejector is associated with a specific piece would not be very practical since the weapon would be in the final stages of assembly. Halting assembly at this point to harden/temper the ejector would be counter-productive