If you are saying it conversationally, it would be "an LBS" - - 'an' before the vowel-sound 'ell'; if you are writing it, technically, it would be "a LBS" because LBS is shorthand for the consonant-sound start of Local. But we all talk conversationally here anyway, so it doesn't matter really.

For the record.

Signed,
Your Editor

P.S. - - Why is it not incorrect to say/write "AN historic moment" even though the consonant 'h' is pronounced?