It would not show up as a “Yosemite Install Disk” from the factory. It should show as “Cruzer”, “No Name”, “Untitled” or something similar. If it is showing as “Yosemite Install Disk” it would seem someone tried making it an install disk for that OS or renamed it.
Yes you can use it between Windows and Mac you just need to format it in a compatible file system. For read and write access on both platforms use exFAT. If you format in a Mac make sure you use MBR (master Boot Record) as the partition scheme. If you format on a Windows computer you can use the default settings and choose exFAT as the file system.
