Historical clue formulations

• Supermarket lines, for short? — 2023-01-13
• Special bars for shoppers — 2022-02-25
• Lines at the cash register, for short? — 2021-06-07
• Supermarket IDs — 2020-10-16
• Scanned IDs — 2018-12-16
• Supermarket IDs — 2017-11-21
• Scannable symbols on store items, for short — 2017-07-06
• Market IDs — 2016-04-02
• Short lines at the checkout? — 2015-07-26
• Modern proofs-of-purchase, for short — 2011-09-23
• Food pkg. markings — 2008-02-20
• Proofs of purchase, often: Abbr. — 2007-06-30
• Short lines at a store: Abbr. — 2004-12-25
• They come in bars: Abbr. — 2001-06-11