Strange. On the same site here is not present words about 1975. Look:
http://topgun.rin.ru/cgi-bin/units.pl? field=8&unit=2376
And here it is written that Has been accepted on arms PRP-3 in 1971 and the batch production has been organised in Rubtsovsk. But this car have developed not in Rubtsovsk, it have developed and have created in Kurganmashzavod (Kurgan Engineering Works) and the batch production has been organised at first there in 1972 and only in 1979 the batch production also has been organised in Rubtsovsk (Rubtsovsk Engineering Works). About it it is written in this source:
http://www.militaryparitet.com/nomen...siabronbbm/10/
Also here still link:
http://en.wikipedia.org/wiki/List_of_BMP_variants