Lou,
It's hard to say. First off, that Blue Book information doesn't sound correct to me. The only real "production" bird's head guns that I am aware of were the Double Eagles, and they were produced after 2002, right up 'til the bitter end" of USFA. In addition to the DE's I believe there were also some ejectorless "sheriff" models as well. USFA did make a few guns with the bird's head grips prior to that but they were a custom, special order item. Examples can be found in some of USFA's early catalogs. I would imagine that some of those early examples were made up from Uberti, or Uberti & US made, parts.
Have you looked at the firing pin? Most all of the Uberti guns have the concave style firing pin. When USFA converted over to all US made they started using the conical style pin.
CJF