This is P-39Q-15 profile from 68 giap, 5 giad:

This profile is based on the low quality photo from Avia Dejavu at: http://crimso.msk.ru/Site/Crafts/Craft20288-3.htm#pics

Same photo but in better quality is also in the book P-39 Airacobra Aces of World War 2 by G. Mellinger and J. Stanaway (Osprey publ.), where board no. "67" looks angular, without rounded corners.
68 giap together with 28 giap and 72 giap belonged to the same 5 giad. Regimental marking of 68 giap (at least) in this time period was blue propeller spinner and blue band on the rear fuselage. Blue color is AMT-7 paint.
Full discussion is at http://massimotessitori.altervista.org/sovietwarplanes/board/index.php?PHPSESSID=5ceegbtocp1f2jfo4fn7sdn5i3&topic=1714.msg14311#msg14311