BID 250/11 Lamberton 
The  250/11 is a secure speech outfit which fitted into the DMU (Digital Master Unit) in place of the blue blanking panel. It was part of the now obsolete Clansman VHF radio fit and enabled the VRC353 radio to send secure speech or 16KB data.
bid250_11_dmu.jpg
BID 250 Digital Master Unit
bid250_11.jpg
 Closeup of 250/11 unit. This is the actual crypto element. 
bid250_simulator.jpg
For servicing the DMU and exercises, the troops trained with the BID250 simulator that fitted into the DMU thus saving the custodian a lot of paperwork. (Photo credit unknown) 
The BID250/11 devicess had an extremely long service life. Although BID/250 was introduced in the early 1970s, some versions of it were still in use in 2009. From 2009 onwards , existing BID/250 units were gradually phased-out when Clansman was replaced by the new Bowman communications system.
In December 2014, BID/250/11 was replaced by the compatible software-defined BID/2510/16.
Contributors and Credits:

1) http://www.cryptomuseum.com/crypto/uk/bid250/index.htm

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Mar 1615