Thanks to Andrew McCabe’s photo stream I can say that one of the bars owned by James Byres certainly made it to the British Museum! (so where are the other three bars?! also hiding somewhere in the BM?!) I now just have to figure its accession number as it does not return in CRRO under RRC 12/1 or under BM collection search for aes signatum.
Paris and BM specimens just for comparison.
Unmarked up side by sides: