I cannot help in any identification, but you can help to narrow it down a bit yourself.

The rear brake cable routing could be a very good pointer.
If the drive chain components are Shimano you should be able to date them, that will help determine within couple years the manufacture, (assuming they are original)
also if the handlebars are original they are normally date stamped, most likely also the stem.
Pull the fork out & see if there is any name or information stamped on it.
Measure the seat tube this opening will help determine the frame tubing.