Pre-postage stamp FREE FRANK letter address (only the front of the envelope remains, the rest has been cut off).
There are two ink stamps, one is red, the other looks more black/brown.  The black/brown stamp is slightly clearer than the red, but is still hard to read.  Helpfully, there is a handwritten date of Twenty six December 1839.  The franking mark looks like it was posted the day after on the 27th.

The addressee is a Mrs Pritchard, 48 Belgrave Square, London.
This building is now the residence of the Mexican ambassador to the UK.

Measures 13 x 7.5cm

Condition PLEASE NOTE: We are not specialist dealers in this particular collecting field, and as such, we are unable / unqualified to give industry standard definitions of condition; also, our terminology may be incorrect so please view the photographs carefully.  This item has some staining to the paper and a short closed tear at the lower right.