[Dénes Bernád]

It's a pleasure to answer your challenge, Mr. Seaplanes. I am always keen in engaging into discussion on the topics I research, in the hope that all of us can learn something new.

There were three distinct avenues the Hs 129 entered in service with the Royal Rumanian Air Force (ARR): aircraft loaned by the Luftwaffe to Corpul 1 aerian (the 1st Air Corps, the ARR's main combat element on the Eastern Front), aircraft purchased directly by the Rumanians and aircraft captured after the about-face of August 23, 1944.

The vast majority of Hs 129s sporting Rumanian markings fall into the first category.

Here is the general statistics - taken from an original Rumanian document - of all the Hs 129B-2s handed over by the Germans to Grupul 8 asalt (the 8th Assault Group), part of the aforementioned Corpul 1 aerian, between June 16, 1943 and August 23, 1944:
Handed over initially: 35 pcs. (at the time Grupul 8 asalt was formed),
Handed over later on, during operations (in 14 months): 122 pcs. (new) and 84 (repaired).
Total: 241 pcs.

Out of this total number, 43 were lost and 166 were returned to the Germans. The 32 pcs. existing on August 23, 1944 were ‘kept’ by the Rumanians and used in combat against their former owners in the following 9 months.

There were 28 Hs 129s that represent the second category and about 14 that represent the third category.

I have most of the Werknummern of these aircraft, so the possibility of large scale counting error is excluded.

Therefore, in closing we can approximate that a total of 241+28+14=~283 Hs 129B-2s were at one time or other wearing Rumanian markings, making it the German aircraft type most used in ARR (more than the Bf 109G!).