Thanks for the pictures, but it appears your key is the newer style with removable head. The OB key is different. Head doesn't come off and case is square and bigger. The battery I bought based on the OP was way too big by 1/8 inch all around - maybe more.

Anyone do the LED conversion on an OB key?

PS. I added the extra picture from Roger with the metal crest added as a side note. I bought the same crest(s) from him so my OB key(s) now has a metal crest like the new style keys. Looks cool IMHO. Now I just need, um, well, want, a brighter light

 

It uses the same battery so it should fit the same. It is not supposed to fit into the button like the original one did. You can also use the BR1225 it will be a little bit bigger than the 10 series battery.

 

Post a photo of the inside of your key so we can see the difference in the compartment.

 

Here is inside view.

 

I think you may be better off going for a 1.5v LED and keeping your same battery due to the contact location.

 

Do you know the model number of the 1.5v led? Will it still be bright? Is it at radio shack?

 

You will have to do the leg work for a 1.5 volt conversion

 

I'll give it a shot.