Help to identify arm board and arms it can accommodate

[Diaspora]

New to this forum and I’ve made a stab to see if my question has been formerly addressed, but this is a fairly specific piece of hardware. This removable aluminum arm board came with my Spiral Groove SG1.1 when I purchased it years ago from a dealer in Japan. The table came with a Graham Phantom L with a Leica bayonet-style arm board. I’d like to consider adding a second tonearm to the table now but am not sure the range of arms this is meant to accommodate.
I’ve included two photos. The long end of the base “points” at the platter when mounted. Dimensions are ~ 6cm x 9.5cm. The holes are 4cm apart at the short end and 6cm apart on the long end.
If you can help me identify the board’s range of tone arms (or specific application) it might accommodate I’d be grateful.
Diaspora

 

[Solypsa]

I don't have dims in front of me but looks like an SME slide type cutout

 

[Yeti]

This is the template for the SME compatible mount for a Korf SF9R if you want to check the hole spacings. SME themselves want to sell their template but the Groovemaster one has the same hole positions.