I always forget about this thread... Nothing unicorn about a Gillette Knack but this one is: the super rare color red Knack! Made in Mexico. T-4 date code = made in the fourth quarter of 1973.
The only Unicorn I ever owned - the Butler Safety Razor: A detailed description can be seen here: https://razors.click/razors/ButlerSafetyRazor/ I found it for 5 British Pounds on eBay ("Unusual razor" was the only description) I then showed it to a serious collector with no intention of selling it, just to get some information. He offered me a boxed Schick Type A repeater, a silver-plated Collins rotary razor and three other razors before I caved in. The guy has been collecting for many decades and had never seen one before. I think he got a good deal.
Maybe one of the rariest Gillette razors out there. This is the only example I've ever seen. A N3 Slim Adjustable not only is the date code part of the reason it is super rare but the razor head also happens to be a Super Adjustable. This is a bona fide unicorn that is so urcy almost no Gillette collectors even know of it's existence. With that said unicorn may not automatically = desirable or collectable.
Put a horn on them and they could be. Honestly I have no idea abut them but if they never did make them for non incarcerated persons then the likelhood of many of them existing should be low.
It has been awhile but another razor that is solidly in Unicorn territory is the Personna Precision Micrometric adjustable. This one is a Gibbs copy that was made in England and can take a regular DE blade without modification unlike the earlier Gibbs adjustables.
Apollo Mikron 1. Mikron 1's are unicorns. When you see them they have a metallic handle - this one is black and the only one that I've seen. The first picture is what I bought and I assume that the broken black piece of handle is correct. I turned the "new" handle out of Nylon so it's unlikely to break again. It's about as best as I am going to do with my machining skills.
Some later model Gibbs razors that take regular DE blades. The earlier model ones are common but these later model ones you almost never see especially the click pen flip top adjustable. This one was labeled a No13 and is a differential razor head. This is I think the is the rariest Gibbs razor out there and in my opinion firmly in unicorn territory. This is the click pen flip top adjustable. I will post better pics once the one I bought arrives.
Yes it is, but I wouldn't read anything into it. I've seen images of the brass ones in this case as well. EDIT: I thought that the Gibbs 9 was here already. (But it has been a while)