The DELTA is a genuine Sinclair ZX-Spectrum + which was sold and exported from former Yugoslavia
Reportedly they bought the unsold stock from bankrupting Sinclair Research.
They removed any references revealing machine's origin:
a) original Sinclair logo was disguised with a thin plastic plate with the word DELTA
b) a spectrum symbol on the right side of the machine was also removed
c) and a "Made in United Kingdom" sticker was there to cover the copyright on the lower side.