This is interesting. I had a rifle virtually identical to this, It even had the aluminum inlays. I never could figure out who made it but this was back in the 80's and no internet. The caliber is what really interests me. Mine had a 1-1/4 inch across the flats barrel and was only 25 caliber! I thought it odd to have that heavy of a barrel for a 25 caliber rifle. It was a tiny bore. It was also very heavy.
The lock was marked Goulcher like yours but on the underside of the barrel was stamped "Remington" which confused me even more.
It otherwise looked a lot like this rifle however.
Someone later told me that Remington made barrels for sale much like Golcher made locks and that the gun was somewhat similar to an 1850's version of what we do today meaning buy pre made parts (barrels. locks, etc) and assemble them.
I still never figured out the purpose of that huge heavy barrel for such a tiny caliber.
I should have kept that rifle but someone with enough money wanted it more than I did.