Can someone please tell me where to look for information on part #(1P)50001864-01

This item is a rs232 RF modem. I cannot match the items part number to anything , anywhere ?

That is just the RF modem part. The actual overall orderable part was: http://www.digikey.com/product-detail/en/digi-international/XM-C91-2P-U/602-2323-ND/4515266

They were also sold in packs with an antenna, power supply, USB and serial cable.
http://www.digikey.com/product-detail/en/digi-international/XM-C91-2P-UA/602-2324-ND/4515267

I believe this product is now end of lifed so as you can see is only available in limited quantities from some distributors.