This is a twin/duplex cable of varying length with 100/140 um "multimode" cores and SMA-906 connectors. SMA-906 connectors have the stepped center-pin, compared to the SMA-905 which is a simpler straight pin. It's used, for example, by the LAN Bridge 100.

For additional information see pages 169 through 335 (of 452) in http://www.bitsavers.org/pdf/dec/comm/EK-CMIV7-RM-005_Communications_Options_Minireference_Manual_Vol7_Aug88.pdf

Probably it has an orange sheath so it would be somewhat distinctive in your tangled pile of cables :-}.

Thank you for looking,

paul