GENERALLY:  The Roumanian Peabody-Martini, is nearly identical to the M1874 Turkish Peabody Martini and both are very close to the British Martini-Henry Mark I.  This model is presumably chambered in the 11x59 (or 11x60) Roumanian cartridge which is very similar to, although, again, not identical with, the .45 Turkish.  The Roumanian Peabody-Martinis were manufactured by O.E.W.G. in Steyr, Austria.  The Steyr markings (an ornate proof and cartouche about the size of a quarter) appear on the left receiver wall as well as on the butt stock.   The Romanian Peabody is otherwise difficult t distinguish from either the Turkish or the earlier British Martini-Henry.

PHOTO:  The above rifle is an example of the M1879 Roumanian Peabody-Martini.

DISTINGUISHING CHARECTERISTICS:  Steyr (O.E.W.G.) markings appear on the receiver wall as well as on the butt stock.  Also, a roundel marked  "Amata Romana" & "Arma Md:1879" appears on the right side of the receiver.  The rear sight is much closer in design to the M1867/77 Austrian Werndl (surprise) than to any British or Providence Tool Company product.

MISC NOTES:  In 1868 Romania adopted the M1868 Romanian Peabody, an outside hammer military Peabody rifle that very similar to the rest of the military Peabody family of rifles except for "Modelo Romano" markings on the receiver.  This rifle was chambered for a unique .45 Roumanian Peabody cartridge which was NOT, as has been speculated (including here) the same cartridge as the later M1872 Turkish Peabody-Martini.  The rifle illustrated here, the M1879 Romanian Peabody-Martini, may also chamber the earlier .45 Roumanian Peabody cartridge, as evidenced by the letter below.
 

I received this wonderful letter from a visitor to the site:

Subj:  Romanian Martini
Date: 99-11-28 17:11:19 EST
From: r.horsfield@virgin.net (Roger Horsfield)
To: kdcolospgs@aol.com

1) From what I have managed to find out non of these were made by Peabody, all of them were made to Steyr. Contemporary references refer to it as "The Romanian Henry Martini".
2) The Turkish cartridge will not quite chamber, the body is slightly too large. The British 1874 Gatling cartridge is slightly small in the body and will chamber. However the Westley Richards No.2. musket cartridge appears to have exactly the same dimensions as the Rumanian Cartridge. I have copies of the original drawings if you would like them.
3) My rifle is in quite good condition and when my friend who has a digital camera can come round I will send you some photos.
4) Main differences from the British Mk.1. and Mk.2. Martini Henrys are:-
 a) The Knox form is a completely different shape being flat on the sides and not on the top.
 b) The back sight has a circular hole in the leaf, as well as the usual V.
 c) The left side of the action has the Styr roundel, date is 1883, (looks the same as the Guedes) and a very faint roundel on the left side of the butt.
 d) The right hand side of the action has a roundel "Amata Romana" & Arma Md.1879.
 e) The fore end does not have the transverse pin thougha lug on the under side of the barrel nor does it have the hook of the Mk.3. British Martini Henry.

Any other information you require let me know.

Yours  Roger

"Amata Romana" & "Arma Md.1879"
Right side of the M1879 Roumanian Peabody-Martini receiver
 
 

Right side of the M1879 Roumanian Peabody-Martini receiver
 
 

Right side of the M1879 Roumanian Peabody-Martini receiver
 
 

Left side of the M1879 Roumanian Peabody-Martini receiver.  The model
designation roundel appears on the right side and is shown in photos above.
Interestingly, Walter states that the rifles were produced by
Waffen-und Guss-stahl Fabrik, Witten an der Ruhr in 1879-1880, but the
above Styer roundel is clearly dated 1883.  I have no explaination.