new member with unusual marked No 4

[waldo82]

I've been reading and did email Brian. He was very helpful. Shim probably wasn't the right word, it was just some extra material between the bolt head face and the gauge to determine how much excess space there was - no intention of attempting to fire it that way. ...that would be very bad. Thanks again, all.

To the spare bolt comment - the receiver was purchased as just a receiver and barrel, nothing else. I've been collecting parts to try to restore the rifle back to working order.