Kermit,
Not as nicely done as the DeCamp/Getz horn, but is this the type of measure your talking about?
These are all interchangeable tips for these horns
I have had a lot of horn tips with the conventional wood plug split on me over the years due to moisture, temperature, etc. causing a lot of stress in the horn spout. Now I always machine a brass insert for the tip and use a fiddle peg reamer to get a water tight fit to a standard fiddle peg. Or, I machine a brass insert that is threaded 3/8-24 and make a variety of interchangeable tips to use on the horn. I wasn't sure I would like the brass cap / powder measure ones I made in the pictures above, but I now find them very handy. I made a few out of antler and /or horn, but I gave them away and don't have any pictures. On those, there is no brass showing when the cap is in place.
I never thought of (or had ever seen) a plug with a cup on the outside end. Very clever, these Americans...