So... does "if slave.[variable] > 0" work for any specific reliable variable? There's a variable for days spent in my household, right? That one would be 0 for newly generated slaves or ones I caught that day, but higher than 0 for slaves I've owned longer than a day?
What I'm basically after is switch the slave's reaction to me perusing them at the auction, based on whether they're familiar with me. So I don't care about first-day slaves at all, but about slaves I sold after molding them a bit, basically. (I routinely sell and rebuy a slave to get upgrade points and a free(ish) brand. I don't think a slave like that should react to my presence the same as a slave who's never been in my house.)
Also hang on, slaves at the auction house have a stress level of 0? That seems... interesting, from a worldbuilding viewpoint. I might toy with that one.