Essex Regiment ( TANK)

[Middlesex1957]

Hello . Here is an Essex Regiment ( Tank ) cap badge .
White metal appears to be discolouerd on the obverse but nice on
the reverse .
This badge possibly wouldn't be one of those which were buried in dry
cement , then dug up and cleaned with some chemical causing a
discolouration ?
We read that this happened some time ago and we're not expert badge
collectors so have no way of verifying as to the validity of this .
Thank You .