Welcome,
The JA30 is just confirming that it was actually made by Janome. The Japanese machines usually have a JA and/or JC number that indicate which Japanese manufacturer made the machine. As Mickey indicated, the Japanese did not have records that would indicate the exact year it was made.
I like the hot links that can be included as text, however, with the links that show up as hot and take you to ebay or somewhere else, I am adding the link address for the generic manual ->
http://ismacs.net/singer_sewing_mach...ion-manual.pdf
Some other threads for 15 clones are:
Will the Real 15 clone please stand up
Class 15 clone maintenance
Janie Doe, the 15 Clone - make over
I like the clones as they sometimes come in neat colors and have the drop feed on the bed of the machine. Of course, I like the Singer 15s, too.
Janey - Neat people never make the exciting discoveries I do.
ETA: unless your 66 is a 66-1 or 66-3, as those use back clamping feet, the rest of the 66s and a whole lot of other machines take a 'regular' low shank foot.