Top rivet on US M1917 helmet

[EEMueller]

I purchased a 5th Division painted M1917 for a display. The heat stamp is ZC (E.G. Budd Mfg. Co.), and the bales are solid rivets. However, the top rivet is different than others I've seen. It looks like it was struck with a marred bucking tool. Is this a WW1 production helmet that is just an oddity, or is this post war? Thanks!

[aef1917]

That's the mark of one of the standard tools they used.

[EEMueller]

Thank you very much for the reply.