What is this? Roundel on 1853 Enfield

[ConfederateCanuck]

While researching the roundel, I came across this article on the various markings/proofs on the 1853 Enfields. Not sure if this has been previously posted to the Forums, but I hope you will find it useful:

P'53 Enfield Production Markings

Research Press was established in 1998 with a primary focus on publishing texts on firearms, long range target shooting and associated history.

web.archive.org