Source is polish article in military press:
Tomasz Szulc,Nowe czołgi naszych wschodnich sąsiadów: T-90MS i Opłot-M, Nowa Technika Wojskowa, 9/2012, s.13-14
Tomasz Szul, The new tanks our estern neighbors: T-90MS i Opłot-M, New Military Technology, 9/2012, p.13-14
BTW: Whole article is very interesting and compare Oplot-M and T-90MS.
Ad rem:
Previously there was no "T-90" tank but deeply modernisated T-72B model 1989 (Ob.184) whit well known armour. The lat T-72 version from Soviet Union was named T-72BU (Ob.188) -this T-72 modernisation first time in Soviet UVZ got normal quite advanced FCS taken from T-80U those FCS was "Irtysz" 1A45T. And this was the biggest difrence between T-72BU (Ob.188) and T-72B model 1989 (Ob.184). From propaganda and marketing resons they changed T-72BU name on T-90 in 5 october 1992. But it was still the same T-72B model 1989 whit cast turret and well known armour.
First foregin export was for India in 2001 while India got 42 redy tanks named T-90S (Ob.188S) whit cast steel turrets -so armour on T-72B model 1989 level.
The second batch in 2002 (82 tanks) got welded turret whit diffrent armour.
(...)
Well Im not sure here,but it's sure that india got:
1) 42 redy tanks in 2001 from Russia - named T-90S (Ob.188S) whit cast steel turrets and well known simple armour from Ob.184 (T-72B) (I had describe it dozens time)
2) second batch in 2002 (82 tanks) got welded turret whit diffrent armour -it's technology impossible that those 82 tanks have the same armour like previous cast turret tanks from 2001. So armour must be diffrent, but from the other hand - there is no way* that Russia sold it's "own" armour - it's some export armour version.
And after that we have contract form 2002 about licence prodyction 186 Bishma tanks - and those tank propably have Indian armour couse Russia doesn't sold armour technolgy to India. Af course Avadi factory was unable to produce those tank (quality and technolgy problems) so in 2007 India bought in Russia next 124 redy and produced only in Russia tanks (so whit export russian armour) and partial-redy kits to licented montage next 223 tanks - propably again whit pure Indian armour.
* I don't know any one example when Soviet/ Russia sold armour/weapons technolgy on it's "own" level. All export variants have "E" or "S" names and they are approved for export - they are just downgraded. Only exceptions are then when some weapons sytem is really outdated but still produced in Russia but the newest version is avaible soon. For exmaple:
Russia sold to India in 2001 those 42 T-90S whit cast turret and armour like in Russian erly T-90S (or T-72B model 1989) so on technology level on middle 1980s., but in the same time new welded turret whit new non-export armour was avaible in Russia and very soon was DOI.
Another example - Russia sold to India 3BM42 outaded rounds (1986) - and those rounds is still in service in Russia (and even produced). But in the same time newest 3BM42M (Lekalo) was avaible and newest- newest 3BM60(?) Sviniec-1 was ended both are not allowed for export still, becouse it's newest and top technology.
So it's sure that russia do the same like US and sold tanks whit export armour, or whit really outaded armour technology.