[time-nuts] Sources for Mission Time Clock

[Martin A Flynn]

I am looking for a GMT/GET mission time clock  that has the following 
characteristics:

  * Reads T minus prior to launch or deployment,  T plus after.
  * Second display for GMT.
  * Simulating it on a PC display would be OK, would prefer an LED/LCD
    version for wall mounting

There is a example of what I am looking for in the background of this 
photo: https://www.hq.nasa.gov/alsj/a16/A16_116_13_15.jpg   .   We have 
NTP, IRIG-B, and a 1 PPS source to work with.

Any suggestions on a cost-effective way to accomplish this?

Cheers
Martin Flynn