Possibly ethnographic gun, of European form

[Atlantia]

TBH, I just didn't want to be the bearer of ill tidings again.
This type of gun show up fairly regularly across the UK. Supposedly from various sources, but mostly retailed by a rather 'well known' trader in the UK.
Some of them have been 'rebuilt' from separate parts, many have at the very least been 'restored' prior to coming to the UK. Including the addition of newly made replacement parts.
Yours has a newly made replacement trigger guard and some screws at least.
However, having examined a fair few of these guns, I am of the opinion that some of the main parts are in fact of relatively recent or indeed very recent manufacture.
Which perhaps should not suprise, as they are probobly still used in some places.
As Martin says, they are of 'native' manufacture.

Here is a picture of one selection of examples in a catalogue from 2001.

They were sold in grades ranging from completely 'restored', down to basically complete but needing some light work.
Yours was probobly sold missing a couple of screws and the new owner just put them in.
To be honest, the ones like you have are the better buy if you can finish them yourself.
The completely restored ones tended to be overly 'cooked' IMHO.

The same trader also sold 'sporting guns' from I think Nepal for a few years. There was also the huge pile of similar weapons from the 'Royal armoury of Nepal'. There are some pictures of piles of them floating about, I'll see if I can find you one.