I contacted Rich to find out if there was any new info on the change-over date for the woodgrain ashtray. Although not a direct quote, here's what he had to say (Thanks Rich).
For the Los Angeles plant, cars from 02C have the woodgrain ashtray, and most cars up to and including 01B have black. However, there are holes in the Los Angeles data between 01C and 02C, so there is still a 4 to 5 week period for which we can't be sure of the extent of overlap.
For the Norwood plant, cars from 03C have the woodgrain ashtray, although woodgrain does start occurring sporadically in 01C. However, as there are a number of cases where people have Obviously swapped in the wrong ashtray, which of these during this time period is real and which is not is uncertain.
Note that there is a bit of factory difference in that Los Angeles had a shorter overlap period of no more than 5 weeks, vs. 8 to 9 weeks at Norwood.
Summary:
Black Woodgrain Notes
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Thru 01B LOS/NOR n/a early black only
01C-02B LOS/NOR LOS/NOR early transition
02C-03B NOR LOS/NOR late transition
03C-on n/a LOS/NOR late woodgrain only
Please remember that this is still preliminary data and should not be taken as a final determination. This is an ongoing CRG research report and we welcome additional input. Especially in the gray areas mentioned above. If you are positive your ashtray is original, please contact us.