This is the typical 19 АИЗ 63 embossing on the amber CD 247.5s from Russia, the date is 1963, the letters are Cyrillic for A I Z (Armatura Isolyatora Zavod) which would translate to "Armature & Insulator Factory ", which is actually a fairly common generic term used by Russian insulator manufacturers. This embossing was previously covered here:

[id=138038902]

The last digit "3 "looks like the mold may have been reworked from an earlier date, as the font doesn't match the "digital" looking 1, 9 and 6.

This photo replaces my original somewhat fuzzy posting