Jim, thanks for posting. I found this one the other day and have been discussing it with Ralph. I would say the seller is smiling all the way to the bank!
Here are some of my thoughts on the clock. As can be seen in the auction photos, it is a "tall" model, with no serial number, a unique identification plaque, and some different physical features compared to others that do have serial numbers:
From what I have read in Shenton and other accounts, it seems the first prototype Eureka may have been a "tall" model. This one certainly has key differences from the production version of that model, in particular the balance wheel design and construction. Also, all tall models documented to date with the exception of this one had the patent information and a serial number engraved into the front plate of the movement.
[*]The only models documented until now to use a brass plaque at the front are the short models and even then only those that had the open chapter dial. Those installed with solid dials generally had the patent info and serial number engraved into the back plate for the earlier ones although later versions used a brass plaque at the back.
IF the plaque on this clock is original, then I would say there is a fair likelihood it is one of the prototypes as claimed in the auction, possibly even the one exhibited to the king. It certainly is unusual having the mahogany base with the quite rare rectangular dome. One thing regarding the info in the auction, I have one clock in my data with a presentation inscription of December 1908 so I believe the factory was actually set up earlier that year and not in 1909 as stated. Regarding the point about the presence of a seconds arbor extension, that is present on all the tall models whether the dial and seconds hand were actually installed or not. The dial on the clock has been documented to be on several of the earliest serial number clocks, so it may or may not be a replacement, however, I would think that for a clock shown to the king they would have had that seconds bit feature. Anyway, it is what it is.
One other thing that has puzzled me for years is how in the world did they decide to start serially numbering the short model at "1" and the tall model at about 6001? Did they only plan to make a maximum of about 12,000 clocks? No overlap has been found between the short and tall numbering, what I have in my database include from 9 to 5696 for the short model and from 6181 to 10538 for the tall model, total production based on these numbers was 10,046 clocks. Probably was a max of about 11,000, about 10% above the estimate postulated by Shenton. From other data it also appears they made both the short and tall model movements at the same time over a period of less than two years, casing some as they went and then completing the rest over a period of about three to four years for a total "onstream" time of only six years (1908 to 1914).
For info, my Eureka database now contains data on nearly 200 actual clocks. I'll appreciate seeing any Eurekas posted here for documentation and to help share the info on these interesting clocks.