For my numeral postmarks collections I am looking for a cover with a meter mark with a UK numeral triangle postmark like shown in the picture:
It isn't a meter mark, it's a Postage Paid mark applied by the post office for mail posted in bulk, when the payment is not in stamps. These would always be in red, but would not normally have the numbered triangle which is supposed to be used for printed papers sent at the reduced rate for 'imitation typescript' items.
Use such as you show would be unusual.
Philatelics GB stamps info: http://www.norphil.co.uk
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