That's a 10440 lithium ion cell. It's the size of a AAA battery. Probably bigger than the keyboard needs but they are cheap, standardized, and easy to source.
Or poor quality boards. I know I didn’t use a real slate board until later in university and it makes a world of difference. Really you need both, great chalk and a great board. But when you have both the feel is superb :)
I'm a ADS200 fan, too. Bought one recently after way too many years of using a 30W Weller. Having a big choice of tips is nice. As a bonus, it's made in the US. I've been able to tackle projects that I'd never have even thought of trying with the old soldering iron.
Yeah, in the states we say 4x5, but in either case it’s the most common large format film size. You buy them in boxes and use them one sheet at a time.
My folks and I moved to a town outside Naples in 2000 and had a 128kbs symmetric ISDN. I remember it being fantastic. A huge upgrade from our 56k in the states at time of nascent Napster and online gaming.
The Olympus PEN cameras (and subsequent small cameras by olympus) have a in lens shutter that is simply two blades. The blades have a triangle cut out of each side and form a diamond shaped aperture. In this shutter the shutter blades form the aperture. This design is from at least 1959 with the release of the PEN.