Ok, First, I am no gunsmith. But I stumbled across this "gunsmith" tool on ebay and thought it looks very much like a thread pitch gauge of which I use quite often. So, I am asking, am I correct or is the ebay seller correct?

Vintage ACE Gun Smithing Checkering Tool | eBay
Gun Smithing Checkering Tool. If for any reason, you do not get one. FOR MORE THAN ONE ITEM. located at the top of the page. in most case's it does not take this long though. for your item to reach you.
www.ebay.com