T inside a triangle

[Bunker]

I would agree with Dannyboy53…I’d say the marking in question is an inspector stamp, possibly a post-war Tula Arsenal inspector’s stamp.  I know I’ve seen it before but can’t recall where.  As an example, Tula AKs used the same symbol with various numbers and letters within, possibly a ‘T’ as well but can't recall.  Other countries also used a ‘T’ marking, alone and within symbols but IMO this one has the telltale signs of an inspector stamp. 

As for the hammers…I believe all of the early Tula so called ‘T’ markings are hammers.  All kinds of terms have been used to describe the different hammer variations (e.g., molot, scepter, ‘T’, etc) or молоток in Russian, but IMO they are all some form of a working hammer and not a letter ‘T’. 
 
The very early Tula hammer markings should not be confused with the triangle marking in question. The Tula hammer marking was used on many early Tula weapons with several hammer variations, whether alone or within a circle or within another symbol.  The two hammer examples RM posted are clearly early Tula hammers and here are a few more from a Tula Arsenal M91 for additional reference.  There are several hammer markings on this rifle, some are single hammer marks and some are enclosed in a circle.









I think looking at Plant 536 examples is also digressing a little from the original question.  As an example, the 1945 brand, like the one jjjxlr8 posted, will generally have damage to the top of the left side point of the star. The hammerhead is long with a right-side tapered point and the haft is straight.  The brand had different variations during its evolution.

Specific to Plant 536…it was established in 1942 and the brand had variations of the hammer, not to mention other variations (fonts, stamping methods, etc), which is a completely different topic.  For reference here are several examples of the brand that highlight the evolution and variations.  Again, not really related to the marking in question.