Hello Don.
The site which you quoted - certainly exact enough, but also is not deprived errors. On this site it is possible to esteem well creation history, the basic differences, etc. Though if I am fair I do not know where here the truth, but nevertheless - here on this site:
http://www.militaryparitet.com/nomen...ontanki/10/-in table IS-2M very first a cell - here it is specified 1954. This site contains the strict statistics and the general information. This site contains the help information almost on all to the technician of the USSR and Russia. This site is very often updated and regularly supported. I trust this site more. Also there is an electronic edition of magazine on the military technics let out in Russia -
http://mk-armour.narod.ru/1996/03/02.htm - here too in the second paragraph is spoken about that that these tanks were modernised in 1954.
Best regards