5751 tubes -- Raytheon

In many tube discussions and shootouts, the Raytheon 5751 tube garners excellent reviews. Invariably, it is the 2-mica blackplate version with the unique windmill, or propeller, getter that is discussed--even in the well-known Joe's Tube Lore review, he has a footnote saying this is the tube reviewed. But a 3-mica blackplate, D-getter version exists and these tubes sound wonderful in my CAL Alpha DAC and Jolida 302b preamp. They are even more scarce it seems than the scarce windmill getter version. Does anyone know anything about the 3-mica Raytheon 5751 tubes--when they were made, are they re-branded GE or RCA tubes, etc.? Thanks.
They are most likely made by Raytheon. Hard to say w/o looking. Probably earlier than windmill getter, almost certainly. More scarce? hard to say. THere is much hoarding going on with the windmill types, so difficult to say how many are out there, but they are not that common, and in more demand I'd think.

Nice tubes, in any case. Sylvania made some nice versions of this tube too.

Thanks for the response, Ed. I suspect you're right about them being earlier productions than the windmill types. And you're right about Sylvania 3-mica blackplates too. The Raytheon and Sylvania 5751s are the two favorite choices around our house for serious listening, especially female vocals. As for the Raytheon windmill getter types, they're hard to knock (I just don't enjoy them as much) and have a refreshing sound. I'd love to know who came up with the windmill getter idea and why, and whether it was patented for that matter.