Strange Sign/Monitoring Device

[Matt]

I wonder if anyone can give some insight into what these are/what they are for.

The below was on the wall on the approach to Barmouth bridge but I’m sure I’ve seen them on the wall below platform edge at Worcester Forgate St and University station

Are they for some sort of monitoring or adjustment?

20220822_191522.jpg

[TimBrown]

Apparently these are Datum alignment plates which measure any movement between the track and the structure that the plate is attached to, as per web link below; and I didn't know that either until reading this internet advert!

https://therailwayshop.co.uk/products/datum-plate

[943KHA]

And here was me thinking it was a device for altering the heating on the platform (down for cold, up for heat)...........................................been working under buses for too long!

[Matt]

Thanks Tim, I also wondered if it was an adjustment for something but the actual use now makes a lot of sense given the locations I've seen them in.