Postcard sent by John (the UK). It says:
Temperance Envelope engraved and printed by J Valentine of Dundee, posted St. Andrew's on 11th February 1851.The design was based on William Hogarth's 'Gin Lane'. / A reduction from the original in the National Postal Museum, R M Phillips Collection, Vol. IX, P. 46I had not heard about these Temperance Societies that appeared in the UK and the USA in the nineteenth century. calling for moderation in alcohol consuming (then advocating for legal prohibition).
They printed their own envelopes sold for 1 penny or half penny in order to supporting the societies. Then the buyers would use these for their letters.. Sadly, few of these have survived since most recipients threw the envelopes away even if they kept the letters.