The oval ELG proof mark is Belgian/Leige Proof Hs
It's what they called a reduced format style for handguns.
The exact same mark in a larger size was used on long arms.
It's the Definitive (Final) Black Powder Proof mark.
Used in the time from the 1870 right up to the mid 1920's.
Of course Smokeless Powder was used at the turn of the Century and forward. If the revolver had been proofed for Smokeless/Nitro powder,
there would be another set/style of proof marks from Leige on the gun showing so.
There are a couple of Proof House Inspectors marks still showing on the gun.
One on the rear face of the cylinder and another on the breech end of the bbl/RH side.
These are simple Capital Letters with a very small Star above them.
The Star indicates they were used after about 1877.
Prior to then and going back to the early 1850's, the Star would have been an equally as small Crown.
There is no record of who the Inspector Marks were assigned to AFAIK.
These marks are different from the 'Proof Controllers Mark' which was applied in years later. The 'Proof Master of the Leige Proof Facility' would be another title for the Proof Controller. Those marks are on record an easily looked up.
Proof 'Date Code' wasn't used till starting in 1921.
There should be quite a number of additional Leige Proof Hs marks on the gun. Both on the Bbl and Frame.
The gun looks to me to have been 'scrubbed' of any of those markings save for those few we can now see.
A ser# may have dissappeared with that OR it may be hiding under one of the grip panels on the grip frame.
The S&W grips added for extra neon to try and say it's real.
But the grips look like they needed some trimming around the top edge of the round portion to make them fit the Belgium frame.
There is also 'De-Farbing' when a modern Repro of an Antique is scrubbed of it's Modern Mfgr markings so it then carries the Old Time look. A Defarb usually gets an aged finish applied as well. The Living History folks like the been there,done that look.
Orig Belgian makers mark may be under those grips on the grip frame as pointed out already. Usually just initials. Sometimes in an oval or circle.
If there you can search on the LittleGun Belgian Makers site and sometimes find the actual maker and some info.
Nouvelle page 0