It’s a rare knife so it does have some value, but not a lot given the condition (broken blade). The problem I see with trying to restore it is, what was the broken blade? Most likely guess would be a pen, but it could have been a longer blade.
If you’re looking to sell it, unless you’re good at repairing yourself the cost to repair may be more than it's value.
Tom McCandless (olderdogs1 here on AAPK) knows a lot about older Case knives so you could ask his opinion. He may see this and comment, or you could send him a PM.
If it was mine I’d just hang onto it and hope some day to find a picture of what it looked like before it was broken. Then you could restore it with confidence. I’d also look for Miller Brothers sources - maybe they made a pattern like it in their line.
Others may have different opinions. It’s your knife so it’s really up to you what to do with it.