67galaxie, I don't have any other pictures than the additional one I posted below. This Ford was the last piece I looked at, and I was running short on time. Due to the poor leadership of our ex governor, the interstate is a mess and this 'local' shop is now an hour away. I will call them and see if I can get those pictures for you.
Re this originally being a chamberless gun, it seems it's possible, if I am reading the description of the diamond proof mark with, and without the C. This has both for 12, and additional one for 10.
Here's the description of the 1887-1896 Birmingham proof house marks regarding chambers. Anyone have better info?
1887-1896: This was the first period that fractional gauge sizes were marked between 12/2 (.740), 12 (.729), 13/1 (.719) and 13 (.710) in respect of 12 gauge guns. The word CHOKE was first used to indicate its presence and to distinguish the correct nominal size of the weapon and its ammunition, <b>the diamond mark was introduced. When this latter mark included the initials LC instead of just the appropriate gauge size and the initial С it indicated a long chamber of at least 3 inches. At this period if the initial С was omitted altogether it indicated a chamberless gun</b>."
And here's one additional picture:
