According to the article by Brad Wood published in Sargent’s
7th Edition, the only patterns he has seen having etched stamp are patterns 516-5, 523-5, 523-6, 5025-5, and 557, all prior to the USA era (that would be pre-1965). The tang stamps were acid etched “Case” instead of being stamped into the metal.
I have no idea of the current market price. Recommend you find a copy of Brad Wood’s article if you’re interested, as you appear to be, in Case fixed blade knives. It’s the best reference I know of.
It has pricing guidelines for every pattern, but it was published in 2008 so at least 11 years old.