Source: Yuri Pasholok
something interesting from Yuri Pasholok’s blog. Some of you might have asked where did the changed IS-3 armor scheme come from. Well, it was based on the following drawings – 1945 production series IS-3 armor schematics from Plant No.200
How to read it: lower schematics shows cuts, designated by regular alphabet letters. The upper picture shows these cuts from profile, the lower identifies the spots. Of the cuts, the upper row (two) represent side armor of the turret, the lower row represents front of the turret at spots K, F, E (check the lower picture for exact spots).
The last cut on the right side (that goes the other way than the rest) is the turret rear.