The L2007 is a memory board for the Vaxstation 3510-3520-3540 series. It's a "M-bus" board. From the fact that you say it has 144 1 Meg chips, I will hazard a guess that you have the L2007-B variation, which is 16 Mbytes with ECC. (There's also a L2007-A which is only 8 Mbytes).

P.S. I'm waiting for someone to say "But there is no Vaxstation 3540...", then I have a story to tell!