Czechoslovakian 7.62x54R cartridges - tracer

doing researches on the Czechoslovakian 7.62x54R cartridges I noticed that the tracer cartridge, officially designated as “7,62 - Sv 59” was also produced prior of 1959 which should be the actual year of adoption.

In 1959 almost all the variation of this cartridge were adopted ( all are designated as 59 with different codes for the various type of cartridges) except of course the version with heavy bullet (182 grs and yeallow tip), coded Tz which was introduced in 1951.

Could you explain why the tracer was designated as “59” since it was produced from the early - mid 50s?

Thanks in advance