Buddy,
The Navy stock is approximately an inch shorter than the Artillery version. The Navy stock should have a medallion screwed to it. This medallion was where the unit designation was stamped.
The stock irons are virtually identical as far as the ones I have seen, although markings may differ.
Here are the photos of a couple stocks that were auctioned in the last year or so. The top stock and the closeup of the disk are the same stock.
regards,
John
http://boards.rennlist.com/upload/navystocks.jpg