Mine has "-MOD. 90-" stamped next to the patent dates just ahead of the rear sight position on the left side. Mine's a later model with notched receiver, and I don't know if they failed to stamp the model on earlier versions or not. Mine actually has a large number of patent dates listed up until just before WW I. Since yours has just the one patent date, I'm thinking it's a pretty early one.
If Jim is right that you have a replacement .22 LR carrier, it should simply be short inside. It should be possible for a machinist to bore it for .22 WRF. I would consider that desirable to do with a .22 WRF chamber, as I found many years ago that .22 LR's not only aren't very accurate in it, and they tend to pierce rims.
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Last edited by Unclenick; May 18, 2011 at 12:58 PM.