208
Soldered-on RTC batteries (with type covered as a bonus)
(i.imgur.com)
This is a community for designs specifically crafted to make the experience worse for the user. This can be due to greed, apathy, laziness or just downright scumbaggery.
Relevant fact: Most standard non-letter batteries are named after their physical size, for example a CR2032 is 20mm diameter x 3.2mm height; or not a button battery, but an 18650 is 18mm diameter x 65.0mm height.
Nice! Do the Letters mean anything?
Generally the chemistry and any features of the battery.
https://wikipedia.org/wiki/Button_cell#Type_designation
C means Lithium. The R means Round.
The IS IEC spec that defines the coding is 60086-3