The Lengenuity A3000 SCSI upgrade issue 4 has 2 x 25pin D plug interfaces. The empty IC Sockets on the right are for termination resistors (not sure if they are used in the version. The controller is an AMD AM5389PC SCSI controller. The ROM on this card is a Lingenuity SCSI Share v3 ROM.

Lingenuity SCSI Share

SCSI share was a Lingenuity product which was a low cost way of connecting small groups of Archimedes and A3000 computers to a single hard disc. Its transfer rate was up to 54 time faster than Econet. It enabled up to 6 computers to share a hard disc, limited by cable lengths. All computers could load the same application at the same time. It was dramatically faster than using the floppy disc drive. The SCSI Share appears to the user as 2 hard discs, the first is a read-only partition that protects application software and the second is a read/write partition for user files and work space. Partition sizes are manager defined upto the size of the hard disc.

Here is an archive of the Lingenuity SCSI Utilities disc. Please note that in 1990 when the issue 3 mini-podule was released the current version of RISC OS was RISC OS 2.00.
 
Here are the Installation instructions for the Lingenuity SCSI Interface card.