Lense types in EXIF

[Roman]

I wonder how Pentax determines attached lense type. I can read
Lens Type                       : smc PENTAX-FA J 75-300mm F4.5-5.8 AL

in EXIF for example which is correct. Does it only apply for Pentax SMC 
lenses or other, Sigma lense has coding recognized by the camera?

Ideas appreciated,
Roman.

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