What you describe is a Sauer transition gun, probably 10 bore. It is not a sidelock per the true definition. The hammers aren't on the lock but the mainsprings are if I remember correctly. Info is beginning to suggest that it may have been Charles Daly that utilized these odd variant type actions and had someone to build them. I'm sure he was looking at the company's bottom line.

http://www.doublegunshop.com/forums/ubbt...true#Post164135

http://picasaweb.google.com/armthree/2009_09_29#5392666993357265506

Kind Regards,

Raimey
rse