In the 250 SL (early)part book, the lower bolt is listed with a MB part number (127 220 00 71) the upper bolt is listed with a DIN number (000931 012120) according to the DIN conversion book this is a hex-head 8.8 M 12 x52 which means 8.8 is a strength rating, M is metric, 12 is the edge to edge screw diameter and 52 is the length. Dave G can confirm. Hope this helps.
Note - I only have an early 230 SL part book - Edition A, and there is no lower bolt listed