There were 3 variants as it seems, intended to improve upon the concept 1938→1941→1943. So I guess they can simply be seen as one. Wiki gives Production numbers for the 120mm Mortar 19(38) as:
Production:https://ru.wikipedia.org/wiki/120-%D0%BC%D0%BC_%D0%BF%D0%BE%D0%BB%D0%BA%D0%BE%D0%B2%D0%BE%D0%B9_%D0%BC%D0%B8%D0%BD%D0%BE%D0%BC%D1%91%D1%82_%D0%BE%D0%B1%D1%80%D0%B0%D0%B7%D1%86%D0%B0_1938_%D0%B3%D0%BE%D0%B4%D0%B0#%D0%98%D1%81%D1%82%D0%BE%D1%80%D0%B8%D1%8F wrote:The first 500 mortars were commissioned in 1939 and 2115 in 1940.
As of January 1, 1941, 2115 mortars were listed on the balance sheet of GAU CA, of which 15 required repairs.
As of June 1, 1941, the Red Army had about 3,000 120-mm mortars in service.
As of June 22, 1941, the Red Army had about 3.8 thousand 120-mm mortars.
- Soviet 120mm Mortar production.PNG (24.19 KiB) Viewed 30 times
The current poduction is 210/turn.
So if we take the second halve of 1941 (assuming it starts July but I count the few turns in June to that) until April 1945 (including April) we have 47.391 pruduced which in game terms would be done over ~202 turns.
47391pieces/202turns=234.6pieces/turn
Units spawning with those Mortars inside them contain 252RDY+62DAM=314pieces.
If we substract those it is 233.1/turn.
If I take the end date (ending Production in August/September-statement) and say we mirror that with T216, we get to
(47391+(1408-707))/216turns=222.7/turn
Starting Pool:
Pools+first week production (in whatever number you count it)+In Units looks good.
Conclusion (for now), the Soviet 120mm M38 Mortar [ID:789] build limit needs to be increased from 210→~222/turn (at least - if Wiki numbers are correct).
Further interesting is this site: https://history.wikireading.ru/132486