Coal drops - 'engines must not pass' signs

[Rlangham]

I read recently of a sign stating 'engines must not pass this sign' or similar words to that effect being placed on coal drops on the ex-NER system, does anyone have images of these and were they commonplace at coal drops or just certain ones?

[PinzaC55]

I am replying from memory so none of this guaranteed but I think the the only one of these signs I can remember in situ was at East Boldon. They were only provided where the coal drops were unable to take the weight of an engine and I think they were all LNER in origin, consisting of metal letters on a wooden board. I used to own a one from Kildale station in appalling condition and it was painted in BR(NE) orange and white colours.
As far as I remember there was no cast iron NER version though I may be wrong - certainly though I never owned such a sign.