"Open value" variety stamps such as this could have one of many service codes, prices, etc. They were printed on demand using the item to be delivered as a guide.
1LG indicates a 1st Class, Large Item service.
The variation illustrated here has a service indicator type IIA and the date code MA15.
It is printed on the Stanley Gibbons design from the series FT22, image 'Red Squirrel'), commonly known as the Post & Go series "Winter Fur and Feathers".
