The main advantage, I suspect, of decals over the paint is that it speeds up the factory's production process. Applying decals below the clear coating would introduce a slower step, and possibly contamination, into the production.
I have a frame I am restoring, and the old downtube SEKINE decal was long stripped away, with faint ghost outlines remaining. But what's the point of riding a Sekine, if people don't know it's a Sekine?
Luckily, it's not hard to make a simple, lettered decal. I made a photocopy of some mint SEKINE letters to use as a stencil, and found some sticky vinyl paper to use for the decal. With some careful effort, I traced then cut out identical lettering for each side.
Cleaning the frame is a crucial step. I used some toxic-smelling solvent to help carefully dissolve any remaining old decals, and finally wiped down the frame with rubbing alcohol (which leaves no residue).
Carefully, I applied the new decals into the ghost of the old, firmly pressing down the edges to make sure they stick. Et voila! The DIY decals are quite sharp looking, and from a few feet away look factory-new.
|Before and after.|
The seat tube (and frame tubing material) decal would be much harder to reproduce (and more specific to the model year), and I'd have to enlist a professional print shop to make them. Which is exactly what a friend of mine did when restoring his vintage Sekine. He had more than a few sets made, and they are for sale if you're restoring a Sekine of your own. Contact for info.
There's also a shop or two making vintage decals for bicycles- but I haven't seen any Sekine decal sets yet. Velocals.com is good, with lots to offer.
Jim Nielsen from Vancouver has scanned the originals and re-printed sets of the Sekine downtube decals. He has a few sets for sale. Your best bet for replacements is to contact him directly via e-mail: jimbotoad (AT) shaw.ca