Here, this should lay it all out there for you on just what coils Detech makes and which are what. I posted this in the Coil sticky in the Sovereign forum. Scroll down this thread until you see near the bottom a message called something like "A Complete List Of Coils Made By Detech".
http://www.findmall.com/read.php?21,1727373,1773986,quote=1#REPLY
That message has information on all their coils along with pictures of all of them, with the exception of the 5 and 6" solid Excelerators I forgot to stick in there, but does have a picture of the 12.5" to 18" open frame Excelerators along with the rest of there coils they make including the SEFs and Ultimate. While that post is meant for the BBS Minelabs, they make all the same coils for the FBS units and vise versa. Only exceptions being the 8x6 SEF or 6" solid Excelerator are not made for the BBS units, but they do make the 5" solid Excelerator for it too.
You'll see pictures of the 12.5" to 18" open framed round "Excelerator" coils, but those are not the SEFs. The SEFs are also pictured in that thread with their other coils they make. I noticed Kellyco calls them "Excerelator" SEF coils, but I think that's just because they used the same page header where they used to list the round true Excelerator coils. I just searched the web and nobody else is calling the SEFs "Excelerators", so I doubt Detech ever did do that.
Why attach a name of coils that never seemed too hot of sellers to a new coil design that has taken the world by storm? If Detech did do that it would be one very bad marketing move IMO. The 5 and 6" solid Excelerator trash coils are very popular, but the 12.5" to 18" open framed ones you never seem to hear much about despite them being on the market for years. Contrast that with the SEFs only arriving a few short years ago and how they are a very popular among the FBS/BBS crowd.
So if you see any coils being called anything other than SEF that are for the FBS/BBS units as well as other machines in the 12x10 size for example, what you are seeing is just mis-worded descriptions by people. Some call them 10x12's, some see Kellyco's site listing them as "Excelerators" and think that might be a different coil, etc. Nope. All the same coil made for various detector platforms, and the proper name is Detech SEF 12x10, 15x12, 8x6, and some larger sizes.