Those screws seem exceptionally large to be firing pin retainers, and on my guns that have such, the screws come in from the sides. These are really large and oddly placed in my opinion, but what else could they be? I like Rocketman's post. Great creativity.

I take it you do not have the gun in hand or you would have pulled them by now.

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BrentD, (Professor - just for Stan)
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[Linked Image from i.imgur.com]