Can anyone id this? Western Union TWX V Diagnostic Control Panel

Anyone know what this is? I bought two of them today. They're aluminium boxes about 9" tall, 4" wide and 1 1/2" thick. They have a four digit LED display and a hex keypad on the front. On the LH side is a rotory switch to set the BAUD rate (110 to 9600). Also a pushbutton labeled INS and a jack labeled "remote INS". (Any guesses what INS means?) On the RH side is a reset switch and a DB-25F connector. On the bottom of the front panel are four rocker switches labeled "Diag" and "1", "2" and "3" with "TEST" above the 1, 2 and 3 switches. On the back is a label that says "Western Union Information Systems", "TWX V Diagnostic Control Panel", "Type Number 900012/IDP 01 995922", the unit serial number and "Made in USA". There's a place for the date but, unfortunately, it's blank. On the top is a 50 pin ribbon cable header. When I got these they had a ribbon cable connecting both units together but I doubt that they're supposed to be used that way. Note that there's no OFF/ON switch or power connector on thse. They must get their power from the unit under test. BTW TWX means teletypewriter exchange service but no idea what TWX V means. Based on this and the Western Union logo I'm guessing/hoping that these are made for testing teletypes. Joe