04-13-2009, 11:05 PM
I think the -4 could stand for Plant 4 (which was also part of the Philco complex; see my site's History section). The OCT 13 is, without a doubt, meant to mean October 13. The -4 could not possibly stand for 1934 since the Model 90 was out of production by spring 1932.
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Ron Ramirez
Ferdinand IN