JDW:
The "672" probably is the assembly number and if so will be found on other parts. I believe it was in January of 1897 when the choke stamps as seen on your example were implemented. The top number is the diameter at the muzzle while the lower number is the measured diameter at 22cm from the standing breech. I'm not sure, but the mark may have been applied before final proofing and if so, then an enlargement of less than 0.2mm was allowed for final polishing without reproof. I still hold that "PJ" was the mechanic at FN. Nice little puzzle with Krupp steel tubes.

Kind Regard,

Raimey
rse