As you can see, as in the French (and German...) system, there is an arithmetic logic to the numbering of the unit related to a corps.
First of all, every units were numbered in the 20 and 30 series, because the previous ones were attributed to the active divisions (from 1 to 21).
- I Corps had a 31st Reserve Division;
- II Corps had a 32nd Reserve Division;
- V Corps had a 25th and a 35th Reserve Divisions.
Nevertheless, the 30th Reserve Division (I Corps) and the 27th Reserve Division (VI Corps) didn't fit to this scheme. But since there was no X Corps, the number 30 was vacant and could be used. Moreover, the 27th could have been previously in VII Corps area and changed its subordination at one time or another.
So it is not impossible at all that III Corps had one or two reserve divisions numbered 23 or 33, IV Corps 24 or 34, and even VII Corps could have had either a 37 or a 26 or 36.
Additional thinking about the numerotation system of the Romanian reserve artillery:
- I Corps: 51st and 52nd Artillery Regiments (30th Reserve Division, derivated from 2nd Infantry Division), 53th and 54th Artillery Regiments (31st Reserve Division, derivated from 11th Infantry Division);
- II Corps: 55th and 56th Artillery Regiments (32nd Reserve Division, derivated from 10th Infantry Division);
- III Corps: no regiment;
- IV Corps: no regiment;
- V Corps: 61st and 62nd Artillery Regiments (25th Reserve Division, derivated from 5th Infantry Division), 63rd and 64th Artillery Regiments (35th Reserve Division, derivated from 6th Infantry Division);
- VI Corps: 67th and 68th Artillery Regiments (27th Reserve Division, derivated from 18th Infantry Division).
As you can see, the exact numbers for the III and IV Corps are empty (it should have been 57 and 58 for III Corps, 59 and 60 for IV Corps), as well as those for VII Corps (69 and 70).
My assessment is that there were at least three other reserve divisions, hypothetically a 23rd or 33rd Reserve Division derivated from 12nd, 15th or 21st Infantry Divisions; a 24th or 34th derivated from 7th, 8th or 14th Infantry Divisions; a 37th (?) derivated from 1st, 4th or 19th Infantry Divisions.
The blind spot of this thinking is that a reserve division numbered in 27 was deployed in the VI Corps area, whereas it should have been a 26 or a 36.
Last but not least, during my researches, evidences pointed out that at least 26th*, 33rd** and 34th*** Reserve Divisions existed for a time. It should fill the gaps for at least III (33rd) and IV (34th) Corps (and probably VII Corps).
* For 26th Reserve Division, see here: http://www.geocities.ws/dangrecu/D26I.html
3.9.39: formed ?
9.40: grouped around ROMAN.
** For 33rd Reserve Division, see here: http://www.geocities.ws/dangrecu/D33I.html
3.9.39: formed as reserve division.
as of 15.11.1939: grouped in the second line, in VASLUI area.
as in 6.40: deployed on the Nistru, in Rezina area (S of SOROCA).
9.40: following Bessarabia's occupation by USSR, the division withdrew and was redeployed in Răducăneni area (SE of IAŞI)
*** For 34th Reserve Division, see here: http://www.geocities.ws/dangrecu/D34I.html
3.9.39: formed as reserve division.
as of 15.11.1939: grouped in Bucovina the second line, in Cârlibaba area (as Detaşamentul ''Special'').
as in 8.40: always grouped in Bucovina, NE of RĂDĂUŢI.
9.40: grouped SW of FĂLTICENI, with the Detaşament 34 Inf. deployed on the new Bucovinian frontier, NE of RĂDĂUŢI.
Even though there are evidences that these reserve divisions weren't disbanded until January 1941.
"Sicut Aquila" / "Ils s'instruisent pour vaincre" / "par l'exemple, le coeur et la raison" / "Labor Omnia Vincit"