This is a car aerial antenna to radio coax adapter adaptor (interface) cable lead. It has an M10 x 0.75 male external thread (Hirschmann type) on one end and a DIN 41585 female socket on the other. 
Cable length is 25 cm (10 inches).
The screw on male connector is the type most vehicle and aerial antenna manufacturers use where there is a threaded connection on the aerial, as opposed to push-fit jack plug type connector used on many aerial leads.
We can supply extension leads of various lengths at additional cost if required.
Specification:

• Aerial Connector M10 x 0.75 male thread
• Radio Connector DIN41585 Female
  

Equivalent to various manufacturers part numbers, which are no longer available, including: Hirschmann AUKAB 435/17, 820870001,  825870-001, Metra 40-VW16, Bosch Blaupunkt 

8 694 413 973, 8694413973, Autoleads PC5-86, Maystar E110