I would guess 40-45$ USD ? This is the most overbuilt 2 x AA light I've ever seen. The LED is outdated but still plenty bright and functional. The best part: it's NW...
Yea it's a very well built light this one. Unusual as well with the rubber grip. Quite a warm tint and nice beam. Suitable for someone working in wet conditions (rubber grip) and low visibility (neutral/warm tint great in fog rain etc) so maybe a highways worker etc. I gave mine to my dad for work as a highways officer. I paid £25 (gbp) for an old one without clip. It's a desirable light despite its age but more for collectors or those who just appreciate hard-wearing quality. as obviously tech has moved on.
I agree with derfyled it'll probably never hold great value but $45 USD seems reasonable
I absolutely love the tk20! Yes it's output is years behind what you can get now but, it's probably one of the strongest double A lights ever made and I spend a lot of time in the woods and it has not only the perfect tint for woods walking/hiking but the beam pattern is perfect for trails.i really should start looking for another one so I have a spare.