Well I found my answer! These original Peabody Martini large frames were part of the order for Turkey! Seems the Providence Tool Co was not able to keep up with the contract for military rifles to Turkey, so the Turks went to numerous other countries to fill the demand. Among these were the Romanians, the Bulgarians, and of course the Austrians, which is the tie to Steyr!
I purchased this rifle from a ex Army Captain, (his family) who was born in England, and served in the British Army. Before WWI he imigrated to the US, and when the war broke out, he became a Captain in the US Army. He was serving in the Phillipine Islands (Manilla) when he spotted what he thought was a British Martini large frame, in a pile of captured weapons. He pulled it out of the pile, and brought it home as a war souveneir! 
The gun is almost new condition, and has all it's original cartouches on the metal and wood. It also carries small markings on every part, even the tiniest parts! The bore is like new also, so I'll do a chamber cast and see if it's one of the standard Turkish calibers. Probably one of those $2-$5 per round cartridges!
Got a very complete packet of documentation on his unit, Company G, 2nd Regiment, USArmy, Oregon Volunteers. Lots of great info on Capt. Gadsny, and his US service, plus his service in the British Army.

i have four of these, one each caliber............sans birdy!


hahaha...found out your lurking places!

Martini Belgian,
Mine is not marked with the O(E)WG marking, but rather with the "Steyr" name on the receiver and buttstock. The only place I could find a marking of OE with WG underneath was on the lever. All the parts have small proofmarks, or some sort of letter on them, but not the OEWG.
I did a chamber cast with Cerrosafe, and it does not match the measurements of the 500-450 #2, but rather the 577-450. I'm a novice at these, so I can't explain why, but I double checked the measurements several times, with the same results. As you probably know better than me, there's a bit of difference in the two cartridges, enough so that they wouldn't be confused, especially in the rim and base diameters.
Thanks for the info!
Kaintuck,
Are you following me? I know you and Birdy have four of everything ever made! (including tall tales!)

Thanks for that additional info MartiniBelgian! Interesting to say the least. Mine has only the serial number G4xxx on the right side of the receiver, buttstock, forearm, and barrel. Left side is the "Steyr*1880" inside a rectangle with the somewhat "flowery engraving around it. Same on the left side buttstock. 
I sure appreciate your help and patience with a novice to these guns!
Regards!

Just curious I picked one of these up at a farm auction.  Looks like it says CWEG Steyr on the left side just behind the sights. also has 1880 or 188G can't really tell.  Small crown on right side behind the bolt.  on the end of the bolt has stamped GG621.  Right side under sight Y684.  The bayonet that was attached has a small what looks like a shamrock with E384 stamped into it.  Any idea what I have & what it might be worth.  I know virtually nothing about guns but this one looked cool so I bought it.  Thanks, Mitch

If your bore is rough, better reload some gg bullets unless you plan on wiping between shots.  BTW, as this is not a brit martini, those production dates are not applicable.  And as it is a Steyr, it actually is Austrian, not german.  Check bore dia.: a 577-450 normally shoots best with .468 bullets, but yours might be a true .458.