If you're going to a gun show, the hammers will no doubt be tie strapped down.
An easy way to tell is to hold it sideways against a light and look where the firing pin would normally protrude. If its there it's not converted. If it's not there it's been converted.
Another way is to look at the back of the trigger. The factory triggers are smooth all the way up, the conversion trigger has a hump on it where the return spring plunger pushes.
Joe