Actually we do have an accounting for machines produced 1953-1954, just not serial numbers. It came from John R. Folkerth's 1972 business plan.
Actually we have production numbers for calendar years 1953 - 1965 for the Mark 5. Not specific serial numbers by month, but total machines sold. In the later years they were building to fill orders, not in anticipation of orders.
From a Post I wrote titled: More Shopsmith History and some more questions.... I may be able to fill in some information.
Within the thread I had the production numbers for the 1972 business plan that John R. Folkerth and his backers submitted in procuring financing for Shopsmith Inc. to resurrect the company and production of equipment. viewtopic.php?p=249505#p249505
The business plan was very specific in numbers of machines produced in each year beginning 1949. 1947-1948 numbers were not produced suggesting the MAGNA production records prior to Yuba’s ownership were not in their possession, thus not included in the business plan.
We still do not know officially the beginning of the fiscal year for Magna or Yuba. We presume Jan 1 – Dec 31.
That said, here are those numbers which includes all the missing years’ production numbers through the production years in question. If you adapt the interpolation of serial number ranges, biasing them to the machines sold, it may be helpful.
See attached business plan numbers, and a comparison with your missing numbers work, which is excellent by the way.
I realize the number of units produced in a time period will vary some from units sold (1972 business plan numbers), especially when they were building in anticipation of orders in early years, but as sales slowed, production was to fill orders in later years, as they were ramping up Mark VII sales. The Mark 2 numbers were not included in anything I found, but that too had much to do with declining Mark 5 production numbers as Montgomery Ward had the cheaper Mark 2 made for them primarily, even though Magna American sold it too.
The business plan called it a Mark V, but the production was Mark 5 for many years.