A guy named Totoro was looking for a Timney 510. You might try looking him up and see if he's interested. That one is a later version with a pin holding the sear from riding on the bolt which he was looking for. No idea if he needs/wants bolt release. He's a slow communicator. BTW I recently sold two, one new 517 out of package for $100 and the other a 510 new in package for $125.