I just added a Denecke GR-2 Master Timecode Generator to the Toy Robot Studios list of gear. This unit allows me full timecode capability with the 552 as a standalone mixer/recorder. Previously I had resorted to renting a Sound Devices 702t or 744t, however many projects that require timecode do not also require ISO recorded tracks. For many projects, separate lavalier and boom channels and timecode are all that is required, and the Sound Devices 552 with Denecke GR-2 fit this bill nicely.
This piece of gear will stay in my kit for use as a master clock with the 552 and as a test clock to test internal vs. external timecode when necessary long after I own a multi-channel recorder.