My copy is the very same as yours but I bought it second hand. I don't know when it was pressed but I found on the web 82 as recording date. Even if I have no proof, I think it may be an early 80's press, cause I dn't see it often.
Regarding Plummer, this name is linked with Yabby You and Wackies material. On the YY he is credited as producer. On the Wackies LP it is credited as drummer for at least the Love Joy's Showcase. I didn't find more info.