Hi Murrayscot - The Steel Adjustable Neck plate and the offset dots suggest your bass is a Matsumoku - have a look at the basses at the bottom of this page:
http://www.matsumoku.org/models/aria/solid/sg/19xx.html
The "Steel Adjustable" plates seem to be exclusive to Matsumoku-built instruments (although this is not confirmed) as do the offset dots on certain Gibson copies. Again it's not confirmed but it appears the serial numbers on early instruments (ie pre 1975) are random, so it doesn't seem to be possible to use these for date info.
Rosetti didn't exclusively source their Eros & Eros Mark II brands from Matsumoku though - I've owned two, an LP copy which I think was Matsumoku, & an early 70s Tele which I think was Fujigen. I think some of the later Eros guitars are Korean in origin, but I've yet to have the opportunity to examine one.
Anyway, from your description I think your bass is probably Matsumoku, and if not identical to any of the Aria versions, probably quite similar.
Would you be able to post any photos?
Jon.