Let's say you're a man in a long-term relationship with a woman and either you have avoided asking her about her sexual history or she has not been forthcoming with the details.

What sorts of things might you look into / analyze in order to get an overview of her past sex life? And for the record, this post isn't about whether her sexual past "matters" or about whether you "should" care about it, so any answer along those lines shall be regarded as off-topic.

The premise is that you've decided it does matter but you can't get the information directly from her in her own words.

Do "slut tells" exist and are they actually effective indicators of anything? Do some "slut tells" make themselves known naturally or do you have to do some probing and a little n-count calculus? Red-leaning men never seem to get tired of repeating the rule "Take the number she gives you and multiply it by three". Do any other patterns like that exist, perhaps some more subtle or less intuitive ones?