This East Geman made derivative of the original zeiss sonnar 135mm f4 has classic status. There were a number of slight variants to the lens over the fifty years + it was made, including the "electric" (pic) which had contacts. The version pictured with a 4 digit serial is, according to allphotolenses, considered to be the best one. There are two other review pages for versions of this lens:
Read more at: https://www.pentaxforums.com/userreviews/carl-zeiss-jenna-sonnar-mc-135mm-f35.html#ixzz623357fel