I'm reading a 2008 JoFMarkets paper by Shkilko et al. with title "Locked and crossed markets on NASDAQ and the NYSE" in which the authors investigate the determinants of locked and crossed markets. Their data is 3 months (October to December 2003) of quoting and trading (from TAQ database) for 100 NYSE and NASDAQ stocks.
In the paper the authors talk about "autoquotes", certain 100 share size limit orders that "... inter-market participants are not required to honor and can trade through them, as they are likely to be placeholder (non-economic) quotes."
Can anyone clarify what are these limit orders and whether they still "exist" in today's equity markets?