I was comparing them against other obvious l's as in Yel on the page where the l goes a lot higher/straighter or with a loop. It may have been because the l was on the end of the abbreviation or maybe not.
Anyway they're submitted now as Bck but as I said I would accept that & Blk in review. Hopefully others will do the same. ( even though there doesn't seem to be a lot of reviewing going on at the moment).