The Custom Shop serial number stamp is done with a solvent ink. I believe the factory stamp is at least under 1 layer of the lacquer clear coat, but it's hard to tell. It ends up looking pretty much the same whether you do it over or under.
For Ink
StazOn makes a decent solvent ink that comes with a stamp pad, it's cheap and it can be bought at a craft store, but solvent ink will work.
Any of these inks will get the job done
Black Ink
StazOn Jet Black Multi-Surface Solvent Ink
StazOn Piano Black Pigment Solvent Ink (piano black is slightly more opaque than jet black)
White Ink
StazOn Snowflake Pigment Solvent Ink
I've also been working on a custom made ink to offer here, it's almost ready.
Many Custom Shop serial numbers are staggered, misaligned, smudged, under inked, over inked and some are just plain messy, LOL. So it won’t matter if you screw up a little bit, it'll still look authentic.
It does take a little practice getting your hand to apply the perfect amount of pressure and takes some time and patience to cut out the digits and stick them to your stamp block, but it should be a fun little project for you. I recommend practicing on lacquer painted scrap wood. If you plan to put a thin layer of lacquer over it, practice that also. If you run into any problems, need help or have questions, let me know. Thanks
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Custom made black ink coming soon
Custom made black ink coming soon
Custom made black ink coming soon