Approved — date when cover has been approved and allowed for manufacturing. It can be found in the bottom of back side on some of Melodiya covers. Covers with different approve dates could be used for the same records with no any differences, nevertheless.
CM — as a result of low quality of domestic turntables and impossibility to manufacture modern tonearms and cartridges Melodiya invented to limit vibrations vertical component while manufacturing records. Records with vibrations vertical component limited have been manufactured with CM index (Cyrillic letters for SM, Stereo-Mono). By the middle of 1970 higher quality soviet turntable reached the market so this limitation became unnecessary.
Factory — since founding Melodiya company in 1964 records manufacturing has been monopolized in USSR. Records could be pressed on 7 factories: VSG - State Recording Studio, which had own pressing facilities (since 1978 as Moscow experimental recording studio), Aprelevka Factory, Leningrad factory, Riga factory (Latvija), Tashkent factory (Uzbekistan), Tbilisi factory (Georgia), Baku factory (Azerbaijan).
GOST — State standard abbreviation. Records manufacture has been regulated with existing state standards. GOST note confirmed products matching to current technical requirements. GOST appeared on soviet records since 1950, possible variants were: 5289-50, 5289-56, 5289-61, 5289-68, 5289-73, 5289-80, 5289-88. GOST allows to estimate record pressing date. So, record marked as Gost 5289-68 has been pressed within 1968-1973 range.
Order — number of order for printing of cover in typography. It can be found in the bottom of back side on some of Melodiya covers. Sometimes it can help to determine order of manufacturing of different covers within the same year.
Run — number of pressed copies can be found in the bottom of back side on some of Melodiya covers. Note that standard covers run, where name of performer and record title should be inprinted additionally, may be related to draft covers only, not to record titles equipped with those covers.
Sound letters — small "recording saloons" manufactured records usually sold together with postal envelope. They were intended to be used first of all as present for far friends and relatives. Often you could record your own voice on such a record, too.
TU — technical conditions. Intended for export soviet records used to be manufactured not according to GOST, but according to TU, as can be seen from their labels. Probably it has been done to match foreign standards - say, do not use limitation of verical component or follow the RIAA curve. Also, TU used to be applied in 1950s before GOST appearence and.
VIA — "vocal-instrumental ensembles" appeared in mid-1960s USSR as an alternative to western beat & rock bands phenomena. VIA status has been approved by authorities and it gave permission to perfom professionally and be allowed to record for Radio, TV, records. Musically VIAs were close to wide lineup big-beat, easy music with brass section. As ideological dictate against contemporary rock and pop music weakened, by the beginning of 1980s many bands appeared, that played in modern genres without use of "VIA" title. So "vocal-instrumental ensembles" became an anachronism in a few years.