The Lambda 8300 is basically a ZX-81 clone. Made in Hong-Kong (by Lambda Electronics LTD? DEF?), it was designed as a cheap computer for initiation and was licenced to many companies throughout the world. This explains why the same computer can be found under many different brands and names (DEF 3000, Power 3000, Basic 2000, Basic 3000, PC 2000, PC 8300, Marathon 32K, IQ 8300, Futura 8300, Your Computer, etc.). But on all mainboards is written a generic "PC 8300", which explains why 8300 or 3000 are often used in licenced names.
The system is thus a cloned ZX-81 with a modified ROM (to avoid legal problems), a better keyboard, more RAM (2 KB), sound features, a composite video output and even a joystick connector (Atari compatible). These represent in fact all the upgrades ZX-81 users usually wanted to add first to their system, but all bundled for a cheaper price.
With its modified ROM, the PC-8300 was only ZX-81 compatible with Basic programs. But soon, a ZX-81 ROM was available to turn your system into a real Sinclair ZX-81 machine, being able to run all software including machine code.
Different addons were available : 16 KB and 32 KB RAM upgrades, color (and high resolution graphics ?) expansion, joysticks, printers... The expansion bus is supposed to be compatible with the ZX-81 one (to be confirmed).
Lambda in Norway, by Knut-Ivar Robertsen:
I do believe that the Lambda was marketed in Norway by some sort of "order through mail company" with the name Marathon. A friend of mine had one. He had a memory expansion pack plugged in the bus on the back of it which gave it a total amount of memory of 32kB. It was as far as I can rememberer completely compatible with the ZX 81. We typed in some ZX 81 games in BASIC from magazines on it and they worked fine.
Lamda in Denmark, by Michael Hansen:
In Denmark it was sold as the "Lambda". It was in the shops and a hell of a lot better than the ZX-81 - if you can use the term "better" about a machine that has less computing power than today's average shaver :-)
The main advantage of this machine was the "ghost" and "car" keys... It gave the games an unreal feel of reality, hehe!