[ICOM] What the heck is an OPC-599?

[ADUHAWK at aol.com]

In cleaning out my ham radio closet today I came upon a sealed, never opened 
box from ICOM America parts.  It's an OPC-599.  It's described on the package 
(in small print) as
DIN 13 pin --DIN 7 pin+ DIN 8 pin.  The 7 and 8 female DINs come together 
into the 13 pin male.

It was addressed to me at an old address...I've had it at least 5 years.  I 
think it has something to do with my IC706 MKII and its AT-180 tuner, but I've 
had a bunch of ICOM through the years.  73 and thanks, 
                                                Tim K0PG