Empire

You need to learn to look for the Obvious.

Look at the fore end fasterner.

Now we know that rules were always broken with English Guns but the fasterner being like it is Stood out like a dogs dick
as being a Black Powder gun and early manufacture.

The other ones that caught my eye were it looks like Non Rebounding hammers, and it looks quite a lightly built gun.

It was only then I realised you had said 450 NITRO !!!

I would be VERY suspect about this gun.