Are they IR 164?
I looked through bayonets, only a 1903/Erfurt with this IR. Carter might have others, but i didn't see the IR164, certainly not wartime and 605th are wartime. Spandau/15 have 5-6 unit marked rifles in the database, 3 look like they could be tampered with (gouging around disc scaring etc...); it is something that experienced collectors support its legitimacy, maybe it is, - I will check rifles from around 1903, Jeff Noll and Carter in my library, - if examples surface from around 1903 (as these tend to group) I will update... but a "normal" line regiment still seems unlikely to me, - a wartime IR or unit sure, especially the history of the 605th and Carter's explanation for it, that makes sense, so too specialized units, assault or MG, but a line regiment? still have suspicions..