Late to the party here, but I will give it a go. When you were raised you were imparted with means of recognition for one to know another is a Master Mason. The examination consists of first showing that you have a valid, up to date dues card from a lodge under a Grand Lodge that is in amity with the Grand Lodge of the Lodge you are visiting (The secretary has a book of all Grand Lodges which share Fraternal Relationships.) Next , in PA at least, you will go into the Examining room, prove you are a Master Mason by knowing the forms of recognition, and then swear an oath (in PA) and obligation that you are indeed a Master Mason, at which point you will be admitted to the lodge.
I am not surprised you were not aware of this process, as it was never told to me until I was at the meeting where it was exemplified.