Recently acquired an 1876 rifle made in 1877.  As this is an early variation it would have been made as an open top.  The Cody letter states the gun was ordered with the addition of a “lid”.  The gun has a dust print dust cover on a rail screwed to the top of the receiver.  Has anybody seen an open top with factory dust cover added?  The serial number of the gun is stamped on the bottom of the bolt.  I assume this is because the bolt would be provisioned with the correct extractor to work the dust cover.  Has anybody seen a bolt stamped in this manner?  Last question, the serial number is stamped on the underside of the barrel about midway between muzzle and receiver. The font of the stamping is identical the assembly numbers stamped on the side of the tang under the stock.  There is nothing in the letter referencing a rework.  The only information in the letter pertaining to the barrel is that it is octagon.  The barrel is 23 inches.  Thanks in advance for your replies.