Less than half of 135's had diff locks. About 1/4 of 150s came without also. (150's were essentially equipped as "decked out" 135's) It was an option, definately NOT standard equipment. TO35/MF35 had it as an option also. VERY few came with it installed though. For the most part, 35/135/150's had ample traction to the point they didn't really need it in most cases. This was especially true later in production when the 135 wasn't being built/bought with tillage work in mind.
Over the years, I've bought and sold 43 135's, and 11 150's, plus the 150 of mine. That totals 55 tractors. According to my records, only 14 total were equipped with a diff lock.