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% replaces any number of letters (la% - lake, lamp)_ replaces one letter (ca_ - car, cat)

Crossword clues for Some letter enclosures, abbr. 4 letters:

SASE: Postpaid letter enclosure: Abbr.
SAES: Some letter enclosures, abbr.
SASES: Letter enclosures: Abbr.
CCS: Letter enclosures: Abbr.