ROM number  goes with   size (K) function        
==========  =========   ======== ================
23-115E4    23-116E4    8K       Pro350 bootstrap                  
                                 in MCM68766C
                                 (8k x 8, 24-pin)
23-116E4    23-115E4    8K       Pro350 bootstrap                  
                                 in MCM68766C's
                                 (8k x 8, 24-pin)

http://www.dunnington.u-net.com/public/DECROMs/23-115E4.bin
http://www.dunnington.u-net.com/public/DECROMs/23-116E4.bin

ROM images, as BINARY files.
DEC ROM part numbers all begin with "23-".
The next three digits+letter+digit are the ROM number.
The final letter+digit gives the general ROM type and size:
E4 means  8192 bytes, eg a 2764 or MCM68766

pete@dunnington.u-net.com