Serial connector, parallel connector, monitor connector under the first flap, and something which looks a bit like a 68-pin or 80-pin SCSI connector, but probably isn't, in the second flap, along with infra-red sensors.
Exactly what the infra red is for, I never discovered, but I do remember using the serial port extensively when I bought my first modem in 1998 or 1999. That's how you used to connect to the interweb back then - and how I started uploading pages and images to my website in 2003! You had a little box of lights which made an angry sounding and pointless set of noises when you tried to dial into whatever company you had chosen to provide your internet service, and it all went through the serial port at 56kb (that's kilo-bits) per second!
In fact, even after the Olivetti laptop was replaced by the current BeebMaster PC in August 2003, I still used the same method for getting online, as we didn't get broadband until early 2006.