Strange Harris but-set 23701-201

[dsk]

Hi Never seen one like this, and definitely not sure about how to use it.  Some pictures under. It uses 4 aaa batteries,  It has a "display" where it may light up: ABCDE  LMH I   On the right side it has a switch marked T and M on the left side 2 switches:
One marked T and P and one marked P and R and I

All info are welcome.

dsk

[dsk]

Is it really so strange to everybody here? I am not able to figure out anything about this one 

Finding out about the other one turned out pretty well.  http://www.classicrotaryphones.com/forum/index.php?topic=14196.msg148207#msg148207

dsk

[AE_Collector]

Never seen that one before DSK.

Got a bit of a hit here:
http://pe2bz.philpem.me.uk/Comm/-%20Transmitters/-%20Bugs/-%20Info/-%20Equip/E-108-SpectrumAnal/CraftInstr-Telephone/tmdecraft.html

A data but set is for use on working data circuits where a regular test set would interfere with the working circuit. That is about tge limit of my knowledge though....

Terry