Matt -

I bought the JRC NSC-71M ship's "reserve transmitter" on eBay maybe 9 - 10 years ago.  I'd not seen one before, but at that time I was getting interested in the 630 meter band before it was a ham band (I ultimately got an experimental license and put it on the air).  It seems to be a rare piece (maybe not as rare on the ocean floor) but the price was low.  

I searched for "maritime transmitter" etc as I figured I might find a MF CW rig that was ready to drive a relatively short antenna that I was putting up on my suburban lot.  The JRC reserve transmitter fit the bill perfectly.  I was lucky to come across it before anyone else was interested.

It is crystal-controlled but uses higher frequency crystals divided down (handy).  It is set up ready to go for 472-479 kHz CW ops as part of my 630 meter transmitting station setup.  It has a variometer-based antenna tuner and antenna current meter built in.

I remote control and key the reserve from my main operating desk where I receive on either my TS-990S or a restored BC-453 with homebrew PS/speaker.

You can read about my early 630-meter experiments in this QST article...

Amateur Extra WD8DAS
RadioTelegraph T000000001
RadioTelephone PG1912457
630-meter Experimental WH2XHY

Happy Thanksgiving!