Nice catch Eric!
Looks too clean of an edge to claim bitten off or injury of some type...my guess is it was born that way. It sure was no tail slapper.
Looks like you are missing a spring on that trap? Possibly a four coil system?
About that spring - it is intentional. That’ a heavily modified 85, with a CDR (PIT) pan. It is set up for 4 coil like you suggested, but they were a bit too strong for my taste with all 4 so I 3 coil them. Seems to work fine, no downside that I can tell. I guess it could be argued that it might snap a little lopsided, and jump out of the bed weird, but I don’t see that when I test snap them. Loving them. Been using a version of a tray - actually a bottomless box with the trap on a magnebed inside the box. Swamp wolf got me started messing with them, and I am at over 15 back foot catches in a row without a toe hold or miss with that setup. I don’t always use the box though, I have only made a couple and using them here and there to compare results. This tail-less one I did not use use the box because the landowner said he had a local conservation officer catch one, and some teenagers down the road caught a few, but this one kept coming back, so I was in super stealth mode. I pushed the chain slide under the mud, and hid the trap with weeds right from the start. The landowner says he sees 3 beaver there every day. But I see 1 to 3 muskrats there every day, and when I showed him the tail he said “are they normally longer than that?”. So I don’t fully trust his insistence that he can 100% id a muskrat from a beaver at 30 yards. Im not going to explain it to the landowner because this is a county job, but the feed pile was a 1 beaver pile. I still have that trap there though, because sometimes I am wrong.