Congratulations on your new gun. It looks to be a fair quality Birmingham gun, as others have pointed out.

On the gauge, it may or may not be a 10 gauge. It is not uncommon for 12 gauge guns from this era (and all other gauges for that matter) to have over sized bores, in relation to it's chambers. The only way you will be able to know, is to measure the chambers. It could very well be a 12 gauge, made to use thin walled brass cartridges, and 11 gauge wads. Measuring it will solve the mystery.

“I left long before daylight, alone but not lonely.”~Gordon Macquarrie