Dear friends,
I do not know from where the comment on the P-39 numbers of the 28th GIAP comes from, but I can say that you can find information on the squadron operations in the Pamyat Naroda site, looking at the Journal of combat operations of the headquarters of the 28th Guards IAP for 1945:
As you can see, in the third column there are what I believe are the airplane numbers, if the heading means number of aircraft.
We have rather peculiar numbers indeed, including 01, 09, 073, up to 74 and even 990.
We have photos of a few examples of P-39 with numbers that correspond to the end of the serial, like a number 5:
And also the number 67 of the 68th GIAP that has been the subject of a 66misos profile:
At the same time, in most of the less than twenty images I know, where you can see both the serial and the individual number, the two do not correspond:
So it is quite possible that the 28th GIAP got its strange numbers from the serial, but it would be more reassuring if we could look at other photos that show this correspondence.
Regards
Daniele