I checked another record of this make and it just has the matrix numbers in the mirror, no number that is the same on both sides. So it makes sense that 1937 can be the year.
"ЛЭФ" used to engrave it on its records of the pre-war times.
But it's the year of issue (not record), and there's no siutable line to place it in, so Yuri moved it to "Additional Numbers".