Loafers are my favourite shoe. It helps that you can get plain and tasseled. Being my age, I am second generation MOD/Two Tone kid, they appeal because they looked so right, and worn by one of my favourite bands ever The Specials.
Two Tone was it MOD? But hey what it did do was bring loafers on to the feet of many young people. The proper ones cost a fortune then and still do! But the quality is so much better.
The original Loafer was designed just before the 2nd World War and has its origins in Norway. Norwegian farmers would wear a shoe when ‘cattle loafing’, hence the name. The shoe developed further in America by the company BASS, and they called them Weejuns, after the Norwaygians. They added the all important strap across the front of the shoe.
The term ‘Penny Loafers’ comes from prep school students wanting to customise their loafers, the penny being wedged in the front strap.
The Loafer look for MODS, I assume, comes from the Jazz players, meaning the Blue Notes lp etc. and because of the college boy look, ie, Harringtons, Levi’s and Loafers. A defining look even today.
There are several makers these days as you would expect. Prices in the UK vary a lot.  You can buy an ok pair for about £50, but spend a bit more and go for a old school make and you can feel the difference. BASS Weejuns are a thinner shoe, where as the Loakes have a more sturdy look and feel.