No problem, crossedchisles. They are indeed a pleasure to own. I was told by Purdey themselves this information:

I have looked the 12 bore Purdey hammerless
self opening ejector gun no.16510 in our records & have found the following
information:
Completed in 1899 for W. H. Bass.
This gun was made to match Purdey gun no.15789 which was made For Mr W. H. Bass in 1896.
29" barrels, 2 1/2" chambers later made 2 5/8", chokes right cylinder left modified choke.
Original stock length 14 3/8" mid.
Original weight of gun 6lb 8oz.