I don't have one myself, but am wanting to obtain the software to reverse-engineer it so emulation of the boards can (hopefully) be added to WinUAE.
It's a two-board expansion chassis which takes Zorro I form-factor boards and has space for a hard disk. I think it came with a RAM/clock board.
There is some info and pics at:
The PAL Jr itself:
http://www.bigbookofamigahardware.com/bboah/product.aspx?id=1361The link on that page "Image showing interior, without installed cards" shows the RAM/clock board inside. The link "Image showing slots, with cards installed" shows two additional cards installed, the "Garganturam" RAM board and the C2-ML HDD controller.
"C2-ML" ST-506/SCSI hard disk controller (hardware-compatible with A2090):
http://www.bigbookofamigahardware.com/bboah/product.aspx?id=1165Garganturam RAM board:
http://www.bigbookofamigahardware.com/bboah/product.aspx?id=976(Note the "Hi Res Version, Back of Garganturam" pic is actually of a C2-ML board.)
It seems both those boards were actually designed by Commodore. [Calling the HDD controller "C2-ML" is a bit of a misnomer, since that text actually appears on both the HDD controller and Garganturam boards.]