True, that being said though, I've actually included my years of training and rank on my resumé. I reckon it's a valuable thing to list, in terms of reference to life skills or character. BUT, I wouldn't expect them to see it with wide eyes and instantly go... "YOU'RE HIRED!" XD
I think it can be appropriate depending on the circumstances.
However, it’s most likely to be appropriate if one is trying to get employment where martial arts is somehow relevant. A teaching position, for example, or listing Training history on your website if you open your own school. Perhaps it would be relevant if you are trying to get work in security or law enforcement.
In my opinion, rank below brown belt level is maybe not worth listing on a resume. A total beginner level like yellow belt, I would not list, other than perhaps to mention some “experience” in a particular method, if it is in addition to another method in which you have more significant experience and a higher ranking.
By way of example, I’ve seen websites where the teacher lists every experience that they have ever had in martial arts. It reads very oddly when they do that. I’ve seen things that will list high black belt rankings in three or four systems, including one or two that they clearly founded themselves and gave themselves high rank in. So things in the fifth to tenth degree black belt range. And several of them.
And then they list “yellow belt in Tae Kwon Do” and “blue stripe in XYZ karate” and “seminar with Master JoeBlow in 1994”. Often a whole list of short seminars with a bunch of different people.
In my opinion, none of these things represent any depth of training and I don’t think anyone who has a solid background in martial arts is going to be fooled by it. If you really feel they are relevant and important, then perhaps list them with a short statement like “ongoing training and exploration in various other martial disciplines as a way of updating my martial education”.
But listing every yellow belt and every seminar on the resume, I think isn’t helpful. It actually reads oddly and screams “resume padding!”
Edit: so to get back to the OP, he is asking if his yellow belt certificate is still valid from over 20 years ago, having not continued training in that particular system. Instead, he trained in another system, earning red/brown belt level. That second ranking is what is relevant. The yellow belt, while technically may not have expired, simply isn’t relevant anymore. Let it go. His training in that system was superficial, and he did it for a very short time as a young child making it even less likely to retain anything from that training, likely no more than a few months, well under a half year would be my guess.
