I bought myself a Christmas present this year: a 1961 VW 1500 parts book.
I've had later copies of both the Type 3 and Type 34 parts books for years now, but they're not as useful to the owner of an early car, since when early parts were discontinued or superseded they were often deleted from the later books entirely. This is a 1961 book with supplements through 1963, so there's a lot of information in it that's missing from the later books. The supplements are useful in determining roughly when certain design changes were made during early production, although they were only dated up through Supplement 6 (May 1962). (Bob Walton has posted downloadable pdfs of the early supplements in the technical section of the 1500 Club website, and has provided estimates of the dates of Supplements 7 though 15 based on the idea that they were likely released one to two months after the changes in production occurred.) These supplements are a great resource to anyone researching the early VW 1500s.
For example, beginning with Supplement 10 (early '63) the parts book lists all the parts specific to the Type 341 1500 Ghia Cabriolet, of which it's said only 10–20 examples were built before the model was dropped. This underscores what a last minute decision dropping the 341 must have been. In addition, some pages in Supplements 9–11 refer to models 351 and 352, the left- and right-hand-drive VW 1500 Cabriolet. While it's clear that the 341 Ghia came much closer to a real production run than the 351/352, this does suggest that a "convertible notchback" was still not completely ruled out until early in 1963.
The '61 parts book and supplements have already answered some longstanding questions I've had about when a few changes to the 1500 Ghia took place:
• The original Lemmerz wheel trim rings that were used on 1500 Ghias beginning in late 1961 (241 601 155 A, also seen on deluxe microbuses and Type 1 Cabriolets and Karmann-Ghias) were discontinued at chassis number 0 050 173, around July 1962, and replaced by the familiar thin-slotted Type 3 beauty rings on 1500 Ghias (and, according to the book, on the 341, 351, and 352!) beginning with chassis number 0 050 174. These same beauty rings (part number 341 601 155) are more popularly associated with the 1500S models of 1964 and 1965. [Go here for more information on slotted beauty rings.]
• Two-piece front and rear window trim was discontinued with Supplement 8 (around August 1962), replaced first by three and then four pieces front and back. Small strainers were also added to the water drains at the rear air engine air intake at roughly the same time.
• A revised dipstick "with sealing cap" was introduced in Supplement 11 (early 1963).
• Accessory wheel beauty rings in four styles were introduced with Supplement 3 (January 1962) and the accessory spare tire tool kit with Supplement 12 (mid-1963).
Nice illustrations too.
There are also some clues about when the early shift and heater knobs might have changed. I'm sure the more I look the more I'll find.