JPS, welcome to AAPK.
You are correct in your assessment of the age of the knife and the common name given to the knife. Here is some additional information. The Case pattern number for your Knife is a 2345 which is commonly referred to as a "Cattle" knife. It might also be referred to as a "Medium Cigar". The "2" in the number 2345 indicates that the handles are slick black composition. The "3" indicates 3 blades. And the "45" is the pattern number which is what equates to "Cattle" or "Medium Cigar". Technically, I believe your knife is probably a 2345 1/2 which would mean a clip blade for the master. Your knife appears to have served someone very well because the blades are diminished by use, sharpening, and reshaping.
I have attached a picture of a comparable 2345 1/2 with long pull blade nick for comparison.
The 2345 is a fairly common pattern and there are many examples available that are in very good condition. Your knife won't be worth much because of the supply of alternatives. If you put it on eBay, my guess is that it would sell for between $50 and $100, with $50 being more likely.
- Case Tested XX 2345 1/2 LP