On this assessment of value...
It is a side lever, a much older locking mechanism. It has likely been rebarreled so it is not a collectable.
Pete
I don't at all think that the 'older locking mechanism' is a 'minus' on valuation.
It's an interesting locking system with a desirable lever configuration.
Also on the re-barreling issue.
If this rifle has been re-barreled by the noted *proper vintage period* British rifle specialists, in the context of this rifle (not a top-shelf Holland and Holland, James Purdey and Sons, etc example...) that's not necessarily
much of a 'minus' either.
If it's not screwed up, and if the bores are good, and if it's regulated properly - and it's accurate, it only makes the rifle more interesting.
If the current owner of the rifle wants to give the Original Poster of this thread a deal on it then great - but I don't agree at all that the rifle is not collectible or that it's locking mechanism configuration makes it undesirable.
It appears to be a very charming and sweet-handling little express rifle, in very nice high condition.
Fifteen hundred dollars would be an absolute steal.
Hooray for the owner and the original poster if given a proper good look at it - then arrive at such a price.
Good things do sometimes happen in this world.
My sense is that if that rifle were to go to auction here in the
US it would get much more than fifteen hundred dollars.
Cheers
Tinker