In the very early (Dec 1964) parts book (which includes up-dates through at least 1969), there are occasionally in the Remarks column plus signs (+) used. Here is a specific example. For item #53 (screw-in rearview mirror) shown on the relevant Group 8 illustration page, the part number (901.731.010.22) is shown on page 8/11. In the Remarks column to the right of the part description the following is entered (typed as shown stacked)
911,911S,912
+++Coupe
++++Targa
My understanding has been that the 1967 normal had a chrome back mirror, the S had a plastic surround, and the Targa yet a different plastic surround mirror. If the +'s in some way indicate differences, why is there only one part number? I searched the parts book for notation about the meaning and use of the + symbols, but found nothing. Finally, the last two questions: a) What do the plus signs signify; and b) how does one find definitive, part-numbered documentation of differences between rearview mirrors among the 1967 models? Thanks, Jim