First, you are going to have the speedo cable attached to the transfer case so the speedo will be correct when in low or high gear in the transfer case.

The Ramsey part on there is a PTO gearbox. Most of theirs were configured to send the shaft out the front to a bumper mounted winch, but this one points out the back. It would be used for other needs in the bed area. A winch mounted in the bed with some poles would be a popular application for this. There could also be some farm type applications, maybe it ran a hydraulic pump or ?

To operate it, you should be able to move the lever forward/backward to engage it, turn the input on the front of the Tcase which is inline with the PTO and see which way you have to shift the lever to get output through the PTO.

Here are the only other mentions I found about them:
http://forum.ih8mud.com/40-55-series-tech/170222-clarification-needed-ramsey-pto.html

http://www.pirate4x4.com/forum/general-4x4-discussion/295314-rockwell-t-223-transfercase.html

I have a 221 in my 68. It has been a good one for me.

1937 GMC T16 468 BBC th350, 4.10
1941 Dodge COE 5.9 cummins, 9 speed roadranger
1947 Diamond T COE, hercules and 4 spd, all original
1955 Chevy LCF 9.0L IH diesel AT545
1962 Corvair (Elsie)
1967 Jeepster Commando
1968 K10
1970 Chevy C50 box truck