Jonnygoose (Bobafett) may be able to help, but anywhere between 1981 and 1985 would be my guess, possibly earlier due to the gusset being in place from the downtube to the seatpost
Like you said, not the best quality bikes but starting to get worth restoring as a lot of us had them as kids - I've got a 1982 Ammaco 202 in my collection still kicking about