Yes Tony, there were different prefixes, for the the “traditional” Leader label: LEA, LED, LEE; and for the “revival” Trailer label: LER, LES (Bright Phoebus only), LETSAM (Our Folk Music Heritage only). The first digit was a price category, followed by a three-digit consecutive number. I do believe Rod Stradling's discography on Musical Traditions and mine on Mainly Norfolk (which is based on Rod's) as linked above are complete.