Backwards indeed.....some of the other information in that post is also inaccurate....
The second dates on double dated M91/30s indicate the date of transfer from the Army to the Ministry of Defence, not a refurb date. Double dated rifles are nearly always marked 'MO' - the 'Ministerstvo Oborony'.
Serial numbers ran consecutively for one year of production - then started all over again. Russian/Soviet rifles had serial numbers for all the same reasons every other firearms producing countries in the world put serial numbers on weapons - to keep track of inventory after production.
Assembly numbers were used to keep track of major parts during production. These are found on the barrel and receiver.
The 'r' does mean year, or god in Cyrillic, but does not relate to Anno Domini or that man with the big Beardwho lives in the clouds. Only Tula made barrels have the 'r'.
Most, if not ALL of the Soviet made M91/30s that are available to us today were refurbished in the 1970s, and are not marked so. We know this from looking at the paperwork that is found in the crates they come in. 1972 features highly apparently.