Question for Electricians

[Ozi]

I'm just starting to renovate a house and have an electrician coming over next week to do basic safety checks and fit a bathroom extractor. I want it on a humidity sensor and independent of the lights. He has asked if there is an existing fan (easy answer no) but there may have been one, there is a vent on the outside wall which may at one time have connected to a fan above the shower. Loft access is really tricky, it's a very low pitched roof on a rear extension, it will take a younger man than me to get in. BUT there is this unknown switch which might once have connected to a fan, it's not your normal light switch but there my expertise ends

Short question - what do you think this is

 

[Spectric]

Whats the other side look like? Hopefully it is obsolete with no power present because it looks like there are no wires to the earth terminal.

 

[Distinterior]

It looks like a standard 3 gang light switch to me.....There does, at least, appear to be an earth running to the metal back box.

 

[Sideways]

+1 with @Distinterior
Domestically, those colours were normally used with two way switched lighting circuits.
If the other side of the plate has two switches, I'd be expecting to find another double or two single switches elsewhere (downstairs ?) working with them.

https://www.ultimatehandyman.co.uk/...#:~:text=Old colours-,goes in the L2 terminal.