I might be wrong but..... I think that's a valve cap that will unscrew. The thing we can see in the picture is, I think, a valve removal tool for a Schrader valve, which is part of the cap. If it is they're very useful. Have you tried unscrewing it or is it stuck fast? My guess is that once removed it will reveal a Schrader valve. If you've got a track pump it will likely have a dual head that fits both Schrader and Presta. I'll be watching this thread closely because I'm as intrigued as you are.