Hi John, I recreate full sets of data cards from the poor photocopy the Mercedes provide. I have recreated hundreds of data cards
and I can say for sure that there are many different styles of data card, far more than are shown in the Tech Manual. The 230SL alone
went through about 6 different styles. Slight changes where made to the size of boxes and the box number referencing.
Box 22 Scheibenwischer was either left blank or filled in with “Bosch”
Box 22 labelled Scheibenwischer no longer appears from Mid-1966. The box is just #22 and is larger in size. From 1967 there is no box #22
just an empty box. It is in this empty box that a vast variety of letters have been printed for example ST, K, R, H, P, Stp, F, c, 2, S, g, Ho,
D, Sch, J, Q, es, m, n.
Unfortunatly I do not know what these letters relate to. On the 280SL data card these letters would appear at the end of box #19 (Tires)
Your data card simply shows “Ho.“ in the empty box.
Box #20 shows the Tire manufacturer, in your case Phönix
Best regards DM.