Wow, thanks. Not having the rifle anymore, just from the pic, I thought maybe it had something to do with the floorplate release. But I couldn't figure out how it might work, remembering only fuzzily how the floor plate dropped down.
I was the one who did the sporterizing on it... the orginal barrel was bent.
I surely regret it now, but at the time, in the 60s, milsurp rifles were being sporterized left and right*. It was "the" thing to do with milsurps. I had it rebarreled to .30-06 with a surplus 2-groove Springfield barrel. I cut out the stock for a Williams peep rear, but the rifle wasn't accurate enough to justify the peep sight --running around 3" at 100 yards --so I took it off and tapped the barrel for a regular open rear sight.
Gave it to one of my sons a while back.
Again, thanks, all! Cleared up an irksome little mystery for me.
Really appreciated those pictures, SMLE !
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* And you could buy them through the mail and at hardware stores and no paperwork. I remember this. I wish all of you could, too.