4K MM15 PDP-15
This is a core memory module made by DEC.
1x 3D core matrix
1x Dioden matrix G613
1x Dioden matrix G614
5x G100 Sense Amplifier and Inhibit drivers
Manufactured in 1970, according to date stamp on 74xx TTL ICs.
Printed labels: "Type=NSO, Assembly No=911134A91, Rev=E, Ser No = 20496"
Looks very good, no mechanical damages to see. The module is a "working plug", but was in stock for 25 - 30 years.
Therefore no function is guaranteed, sold as "defect".
Probably this is the core memory module "MM15" from the PDP-15.
MM15 consists of 4096 18-bit words.
For docs see
bitsavers/dec/pdp15/DEC-15-H2BB-D_PDP-15_EngrDrwsVol2_Dec70.pdf, pdf page 140
DEC-15-H2BB-D_MaintManVol1.pdf, page 26
Other driver flip-chips (G222, G223) are available too, but not part of this offer.