The Lord of the Rings.
1st Edition, 6th/5th/3rd Imps 1956/57/57.
George Allen & Unwin.
Hardbacks in paper covered slipcase.
Hammond p.98.

Two batches of 500 sets issued:

Batch 1 - Slipcases manufactured by C. Davidson & Sons.  Not seen, but probably includes 6th/5th/3rd impressions 1956/1957/1957.

Batch 2 - Slipcases manufactured by Jarrold & Sons.  Pictured.  Includes various impressions dated 1957-1959.

This earliest version of the slipcase can be identified by the presence of the price printed on the label - "63s net the set of three volumes".

The first batch of slipcases may have been made from thinner card than that used for later slipcases.

For full details of this boxed set see the article on The First Boxed Edition of The Lord of the Rings.