Interesting question so I decided to open some boxes.

I have two DL-103r. Both have traces printed with black ink on paper typically used for plotting such things. However the 'older' one which I purchased as broken about 7 years ago to have it retipped, has the number 8521 while the one I purchased s/h about 6 months ago ("It's new but I can't get it to track properly") and I must say it looks unused, has the number 1594. Incidentally, when set up correctly it tracks beautifully.

Interesting!