Polarouters and Polerouters spanned over 20 years of production, and during this time there was a number of caliber upgrades. In short, the chronological order for movements is: 138ss, 215, 215-1, 215-2, 215-9, 218-2, 218-9, 60, 69, 1-69, 71, 72. There is gallery of each of these in the Movements section, and parts similarities and interchangabilities are found in the Tech Info section.
With technical advances prompting the new caliber numbers, and model references being produced over a number of years, often these new calibers seem to have been introduced part way through model reference production periods. For example, the 20365 changed from being powered by a 215-9 to a 218-9 part way through its production, and the 204610 changed from being powered by a 215-2 to a 218-2 part way through its production.
These changes appear to occur at specific serial numbers, with no apparent “transition” periods. By knowing enough of these serial numbers for each model reference, we can therefore track which caliber movement that a specific model reference with a specific serial number should have.
The mid-production caliber changes also seem to have been reflected in the text on their dials. For example, all Polarouters and Polerouter S/H 20214/20217 were powered by a 138ss, and had “Automatic” printed on the dials. However, when the Microtor was introduced to the Polerouter lineup, it was now displayed on the dial.
The very early production 215 calibers (e.g. 10357, 20360, and 20363) began with just “Microtor” on the lower dial. Soon after this was changed, so that “Automatic Microtor” was displayed instead.
When Polerouters changed to being powered by 218-based calibers, any reference to Microtor was removed from the dial entirely, and just “Automatic” remained. This text was then continued into the references with the 69 and 1-69 movements.
Below are examples from the 20360-2, and 20365-1 production periods.
So, by inspecting a Polerouter for its Reference number and Serial number, we can then use the Reference Tables and the dial information to whittle down the movement caliber by which the watch should be powered. A quick trick to have up your sleeve when assessing a potential Polerouter purchase…
Exceptions: It is rare for UG to have made exceptions in their production patterns, but in this case there seem to be a few (but we may well be proven wrong in the future…).
More specifically, with the Polerouter Sub (model reference 20369) where 215 calibers were used, but Microtor does not appear anywhere on the dial.
The Polerouter Geneve line (20375/40375 and 204604/404604), utilised both the 215-9/218-9 and 215-2/218-2 respectively, but we are yet to come across an example from these references with Microtor printed on the dial.
Additionally, all Chronometre-grade Microtor examples found so far with 215 based movements, do not have Microtor printed on the dial – but instead have text as “Chronometre Automatic”.