This is a case for the Sinclair QL QIMSI Gold interface card detailed on the QL forum here https://qlforum.co.uk/viewtopic.php?t=4799

It is a modification of a QIMSI case (https://www.thingiverse.com/thing:6404943) to allow for the extra components and connectors on the Gold version of the standard QIMSI.

The rear port cover snaps into place quite tightly but a spot of glue will secure it for ever.

The us also a version of the cover without working on it.

Reoriented the two parts as best suites you 3D printer.