I've had my Carrera Krakatoa for 20 years now give or take, bought it 2nd hand in 93(?), the groupset on it was pretty much all Shimano Altus A20, and aside from the chainrings and cassette wearing out the only thing wrong with it is a little side to side play in the brake lever hinges (rivets not machine screws), the mechs have never missed a beat.
This is the one http://www.retrobike.co.uk/gallery2/v/M ... 0.jpg.html
I picked up a Marin Hawkhill last year for free and its running Acera X stuff, now I think both bikes are the bottom end of each respective range.http://www.retrobike.co.uk/gallery2/v/M ... X.jpg.html
I'm just wondering where Altus A20 would have sat as I've read conflicting opinions trawling google. Some say its equivalent to Alivio, others Acera, and some say it was the entry lever stuff.