One reason canoe stem profiles often don't look the same is that they are usually photographed from different angles. Stems are also known to change shape slightly over time, especially during repairs and restorations. The bow and stern stems on my 1936 Otca were probably both created on the same form and yet two differently shaped forms were required to accurately bend replacement outside stems for it a few years ago.
It is possible that Old Town's Molitor stem form was changed during the 1920s. A comparative analysis of the stem profiles on all known Old Town Molitors from this era would be interesting but there probably aren't enough examples available to yield conclusive results. I have not noticed any dramatic differences in the ones that I have seen.
Well over 200,000 Old Town build records have been electronically scanned. Some records are probably missing but this group appears to be a reasonably complete record of the production from May, 1906 through November, 1975. Over 14,000 of these have been manually typed into a database which makes this information easier to search and analyze. This somewhat random sample subset is less than seven percent of the total but it does provide a limited ability to extrapolate and make some guesses about the total population. An example of this is shown at
http://www.wcha.org/catalogs/old-town/models.html but the accuracies of these estimates are limited by the small sample sizes. The messages at
http://forums.wcha.org/showthread.php?t=4722 have some more information about this topic.
Therefore, I don't know exactly how many Molitors were built in the 1920s and would have to manually search through over 40,000 build records to count them. There are 16 which appear in the database but this is a small fraction of the total so my guess is that there were several hundred made.
Let me know if this doesn't answer your question or if you would like more details. Thanks,
Benson