As I said I only have three guns with pre 1887 proof marks from England. The I Hollis & Son muzzle loader, a W Richards, 12 gauge hammer breech loader, undoubtedly made by Clabrough, & a W & C Scott 12 gauge Pin Fire.
All of these only have the gauge stamped once.

Most often the bore size will be increased between the provisional & definitive proofs. Even IF this is not the case it still doesn't explain the decimal point in front of the one marking.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra