Really though if another counter sits down at your table, you would probably know in 10 minutes tops if he is a counter also so I am sure it did not take much to figure out.
Over the course of many years, I’ve spotted ace reckoned counters (sometimes before a hand was played), ace neutral counters, ace trackers, shuffle trackers, opposition betters and of course the hundreds of lil old men and ladies with their modest 1-2 spreads being decimated by the house. Sometimes I knew what ace locators were doing without them knowing what I was doing.

There’s a poker player (hope he’s better at poker than he is at blackjack) who also , poorly, counts. Knows his basic reasonably well and has no knowledge of index play.

Now, as to wheather the house knows or doesn’t know if you’re counting or not - in most cases they do - so a copy paste from a post I made last May should explain why the house often lets you go forward

”1. The counter is not good enough and under capitalized to beat the house - let him play
2. The counter is good enough but undercapitalized - let him play
3. The counter is capitalized but not good enough - let him play
4. The counter is both good enough and capitalized - boot him

The house has me pegged at 3 until they don’t