I printed a few of these, numbered the pages and stapled them into a file folder...
http://www.surplusrifle.com/graphics/boundbookpage.pdf
It doesn't need to be an actual "book", in fact, it doesn't even need to be paper, at all, anymore.
Electronic record keeping is acceptable now by the BATF.
If you acquired the firearm BEFORE you had an FFL, disposition does not need to be recorded...even though it might be a "collectible" firearm, it need be treated no differently than any other since it was purchased before you were licensed.