Actually, they hard coded: any Teensy with MTP+SERIAL USB Type...
#elif defined(USB_MIDI_SERIAL)
#define VENDOR_ID 0x16C0
#define PRODUCT_ID 0x0489
#define MANUFACTURER_NAME {'T','e','e','n','s','y','d','u','i','n','o'}
#define MANUFACTURER_NAME_LEN 11
#define...