My mother called her favorite childhood drink as a "black and white." Not the drink featuring coffee liqueur, but milk and chocolate syrup and seltzer. I am to understand that a black and white is a specific subset of egg cream, which sounds to me like a bog-standard no-ice-cream milkshake.

I bet you could get egg creams and milkshakes in MA if you really wanted to (to say nothing of all the trademarked brands of milk-and-flavor slushies), but why bother, when you can get ice cream in a frappe?