This is the 10 elements, it’s the early MD III version
MD III has new aperture lock and improvements to allow program exposure, improved coating. Introduced in 1981. Please note the new domed cap.
Built-in Filters: Normal-Y52-B12-R60
It was later replaced by a MD III version of the previous bigger and heavier 11 elements in 8 groups formula.
THANX to Andrea Aprà for all the informations he shared with me