I'm glad you got the brochures, and it seems like they helped you out some! Did they send you a complete brochure, with pictures of all bikes for that year?
Does your bike still have the reflectors on it? I ask because the reflectors on the front and back of my mixte has the numbers "SAE-A-73 DOT" on it and the other one has "SAE -A-70." I am curious if the 70 or the 73 might be the year the reflectors were made? It would be interesting to know about yours! I realize that IF that is a date code it would only be for the reflectors BUT it it could still be of help!
I guess till Batavus or someone comes up with a database of serial numbers for our Batavus bikes we are left to dig for clues whereever we can!
Al