This is a Long Socket Wrench with Plug Grip from O.S. Engines.
This special glow plug wrench is for use with cowled engines or those
having deep heatsink type heads (car and helicopter engines).
It has an internal grip which holds the plug securely while it is
being withdrawn or reinserted.
One Long Socket Wrench with Plug Grip
Length: 3-7/8" (9.8cm)
– If you need more information, use these O.S. resources –