BR v. B-R ignition coil changeover date

[My68SS]

Hi all, after much sifting through various forums including this one, it's not exactly clear as to when the change from BR to B-R embossing of the coil occurred.
What's the best timline estimate to date for this change?
Unfortunately, mine has somehow ended up with a 429 B-R fitted to it, when it should most certainly be a 293 and probably BR, not B-R

The best estimate I have so far from all I've read on this change, is sometime during the 68 model.
In another thread on this forum, Marty has said that he has seen 68's with BR and 69's with B-R, though another forum has quoted 68's with B-R
All help appreciated.
TIA

[KurtS]

The 293 Delco coil assembly print has the following change note: 9/12/68 - B-R was BR.