I recently attended a bamboo fly rod makers gathering in Colorado. One of the programs was about using water slide decals for signing rods. I was quite interested because my handwriting has never been that good and with advancing years, it has gotten worse. I was quite skeptical, to say the least.
I was thoroughly impressed. The most difficult aspect was selecting the type and size of font to fit on each flat of the hexagonal rod that measures only about 5/16" across the flats (of the hex cross-section), meaning the flats are a little less than 3/16" wide. Once the font was selected and the text entered, printing the decals can be done on either an inkjet or laser (special media, specific to which type of printer). Inkjets require a fixative to keep the ink from smearing during the transfer process, lasers do not.
All that is great, but what really impressed me was how invisible the decal media was once it was in place on the rod. And then, once varnished over, it completely disappeared. I tried really hard to find the edge under the finish but even with various light angles, I could not see it.
I've attached a couple images of the raw (no varnish finish) decal on a section of bamboo blank where I applied the decal, the first just showing it without regard to trying to see the edge of the decal.
The second, I tried to get the light to reflect so the edge could be seen. Work in some areas.
Several years ago, I saw a demonstration of signing rods using the old India Ink "Leroy" lettering sets. I promptly found a set for sale on eBay with the right sized template and bought it. I still have not used it and now that I've seen the decal method, it is likely I'll never use the Leroy.
One could include anything in the way of a logo, text, date, serial number, etc. All it would require for longevity is to apply some form of clear coat over the top to seal and preserve it. Bamboo rod makers tend to use very high quality varnishes that hold up to exposure to sun and water. The printed lettering was not affected by solvents in the varnish, but one would have to test any finishes they intend to use.
If anyone is interested, I can post the URLs to the decal media supplier the program presenter used. He was using inkjet. I have a laser so I have already purchased a small quantity of laser printing media. It was really quite inexpensive and the media is about the only expense. There are small quantities (2oz) of fixative and a "mounting fluid" that aids in sliding the decal around, but they are also quite inexpensive. As mentioned, the fixative is not needed for laser media.