Anyone recognise these?

[3pinplug]

Hi all

Found about 8 of these all close together when out metal detecting in Germany, anyone recognise what they are. They are 12.5cm in diameter and have a single handle on top with two lugs underneath, looks to be a "twist to lock" mechanism?
Thanks
Mark
https://ibb.co/yBS8d6j
https://ibb.co/kMLGL72

[3pinplug]

Hi all

Gave the item a clean following advice I found in case any marks etc onb it, but nothing there. It appears to be a sandy / yellow colour and the locking mechanism is a little clearer now.
Anyone any ideas?
https://ibb.co/2trCSSP