I have seen some franklins in old rattler holders that to me look like they are full bell but they aren't labelled as such on the slab. Were the rattler holders used before the FBL designation started being used?
To answer your question, FBL was not used on rattlers. Check out this link. Google is a wonderful thing.
No worries. It said in that thread they thought sometime in 1997...I'm surprised it's that recent that they started doing the FBL thing.
No, it will be automatically designated on coins which deserve it. It works just like any of these designations (FT, FH, CAM, etc). Brandon, none of the TPGs designated FBL until the mid-to-late-90's. Early Franklin collectors actually preferred to find coins on which "Pass and Stowe" was fully readable (on some issues, this is easier to find; on some, harder). TPGs began designating FBL after a campaign led by Rick Tomaska garnered enough support. Tomaska wrote a very good book on Franklins, but even from very early on he was a shameless promoter in the vein of B. Max Mehl.
I'm glad this came up, I've never been able to remember exactly when it was. But a couple of points about the info in the PCGS forum thread. PCGS began using the green label slab in 1990 and continued using it until Nov. of 1998. The copyright notice mentioned was first introduced in '95. So the '97 time frame has to be pretty close.