As the title says .........

I have a 16,000 ish serial number W C Scott and Son, 12 gauge, SXS,
in measuring the chambers it appears to be a 2 and 3/4 inch gun.
My question is ........was it common to have a side lock hammer gun chambered for 2 3/4 ? I was under the impression that it would have been 2 1/2 inch chambers. there are no proof stamps indicating size.

It does not appear that the chambers have been lengthened but it is hard to verify.

any thoughts would be appreciated.