The Lambda 8300 was a Sinclair ZX81 clone from Lambda Electronics Limited of Hong Kong. It was not an exact clone, as it had a modified ZX81 ROM, but could be fitted with a ZX81 compatible ROM. It came with 2K RAM (expandable to 16 or 32 K), and a sound and joystick port. Specifically, it used a Z80A microprocessor at 3.25 MHz. Unisonic distributed it as the Futura 8300 in the US. The computer was somewhat successful in Northern Europe (mostly in Denmark and Norway) and China, and today enthusiasts still develop new hardware.
Lambda 8300 models are all identical to any other models, but some of them (but not all of it) are released in any country in some parts of Western Europe, Scandinavia, North America and Asia. But some of them are not yet released.
Although, it was also released in New Zealand as well as the Polybrain P118, though it was never a commercial success.
Source: Wikipedia, "Lambda 8300", available under the CC-BY-SA License.
The CPU used was a NEC D780C-1, which is a Z80A clone, and used a modified ROM, which made it only compatible with ZX81 BASIC programs: An ZX-81 ROM became available which could turn it into a true ZX81.
Other add-ons available for this were RAM packs (16KB and 32KB expansions), colour expansions, different joysticks and printers - and it should be compatible with the ZX81 expansions as well...