Skip, the sirens I was thinking of are a cross between a model 66 and 66H or 28 and 28H. The number of ports for the higher tone are different than a standard double tone. That particular version of the double tone is rare.
As to the "H"model high-pitched sirens, Federal offered them in the 60 series and the EW series, all at extra cost. I know how you dislike the high pitches, but Midland PD had a 28H on one of its patrol cars in the '60s which was ear-shattering. I don't know if it came with a specail motor, or if it might've been a 6-volt siren running on 12-volts (as Midland was bad about that), but that one particular siren had a very quick rise to it; and it would hurt your ears. I always wanted one of them ever since and finally got one from the late John Dorgan several years ago, and I latched onto a 66GH a few years ago as well. My only other H model is an EGH.
One last word about the doubletones. It's not widely known, and I've only seen two of them, but Sireno also built a doubletone siren which they called a "dualtone". These were available by special-order only. Now those are sirens that are extremely rare. The two I've seen were both underhood models: the J8A which had no brake, and the J8B which had the brake. Both were painted in a black finish, unlike the gray hammertone color of Federal's underhood sirens (although some of Federal's underhood sirens in the '30s and '40s were black). I had a J8A that I got new back in 1964. A friend of mine in Florida dealt in a lot of used sirens back then, when prices were reasonable. You could get a used 28 from him for less than $50. I had been wanting a doubletone siren for some time. Midland had switched to the 76B underhood doubletones in 1956 and I loved that sound! I had two old sirens that I had acquired: a 6-volt S8 B&M and an old 66 (before they became 66Gs) that Federal called a "junior longroll siren". I traded both of those sirens to my friend in Florida for a brand new J8A. Not long before I made the move from here to Lubbock I loaned that siren to the Sheriff's Posse Jeep Patrol in Odessa. Big mistake! Haven't seen that siren since. If I had known that they would be so rare, that wouldn't have happened. And the sole J8B I saw was on Ebay. A friend of mine in Ohio won it and now it belong's to B&M Siren's owner, Kevin O'Connell. To conclude, Sireno sought to duplicate all of Federal's line, siren-for-siren, but not all would be stock items. The one siren that Sireno built (and there may have been others) that was exclusive to Sireno was called the "Atomic Rocket". It was built "inbetween" their Vanguard series at 8" that competed with the C-series and the 10" ED10 which competed with the Q. The Atomic Rockets were 9". I've only seen pictures of them, so I would assume that tney are quite rare.