The lightweight single hammerless guns and rifles could have been made by Alex Martin but given his multiple addresses in Birmingham for 60 ish years it is more likely it was partly or wholly made in the Trade

All the small side lever rifles and guns were trade made and marketed by H&H, Purdey et. al. downwards

I had one similar to yours years ago by Churchill (Cased) but had it sleeved to .410 before we could hold obsolete calibres off ticket
That fore end was snap off

Period mounts would look best IMHO

Good luck

TH44