There are many features that go into the value of these things beyond caliber...... I’m certainly no expert on evaluations, but to me there are a number of things that go into value beyond simply being the first out the door in a specific caliber.

First and foremost, what condition is it in? Are there any handling marks or is it perfect “like new” condition. What is the model #? Presumably 88B? Side lock or box lock? Is it a PH model or Safari? Does it have plain wood or very fancy wood? Somewhere in between? What is the engraving like? Is it very simple light engraving or is it heavily embellished with deep relief engraving? Is there any gold inlay? Does it have an extractor/ejector selector? etc......

From a collector point of view, I’m not sure the caliber story will have much impact on value.... I suspect many would simply view it as a used modern rifle with an interesting data point. Having said that, all used Heyms commands significant dollars and are quite valuable in and of themselves. Again, I’m no expert in these matters.