So here I am in Italy with a bunch of stuff with Schuko plugs on. Schuko is one of the options here, increasingly widespread, but for neatness and compactness (and it is very neat and compact) the original Italian CEI 23-50 sockets are still installed. These come in four flavours; 10A and 16A with or without earth, although most sockets are earthed. The pins of the 10A spina luce (=lighting) are on the same 19mm centres as Schuko but 4mm instead of 4.8, while the 16A spina forza (= power) has the larger pins but on (IIRC) 26mm centres. This prevents me cheating and plugging Schuko stuff in without the earth, although naturally Europlug fits the 10A gauge.
Historically, lighting and power were often on different voltages and tariffs, so the plugs were deliberately incompatible, stopping you plugging a 127V light fitted with a 10A plug into the 16A sockets of the 220V power circuit. Nowadays the voltage is standard and all from one supply, so manufacturers offer a dual-gauge 'Bipasso' socket which is now pretty standard. Also increasingly standard is the presa unversale or polyvalente which takes Schuko, 10A and 16A CEI plugs, although at two modules width it's twice the size of a Bipasso. It's also deeper because of Schuko's plug recess. Like BS1363, CEI 23-50 uses insulated pins to provide touch-proofing instead of a recess.
Two pics, one of a situation that will keep presenting itself for now: presa Bipasso, spina CEI che si adatta, e spina Schuko che non va bene. Plus one of the view along my drive to work.