Hello Dimitris,
Thank you for your message.
Your "unknown" lathe is of a type made from around 1910 to 1930 (or so...) . Almost all makers of machine-tools at the time produced something similar and, as with yours, it was not uncommon to find a complete absence of any maker's name or insignia. These unbranded machines were often the result of a major dealer or distributor ordering a large quantity on the understanding that no identification was attached - and he would then add his own screwed or riveted-on badge, often in the form of a bronze casting. These elegant badges make tempting souvenirs - looking for tell-tale holes in the bed might give confirm this. Machine tools were often copied and, if your area had a manufacturer of weaving equipment, it's likely that they would be responsible - even a back-geared and screwcutting lathe is nothing as to the complexities of a powered loom and such lathes made a useful fill-in when other sales slackened.
It's not a lathe I've seen before but, from its general appearance I'd guess that it's German in origin - some German companies using Whitworth threads into the early 1900s - and on larger threads for much longer.
Sorry that I can't help further.
Might you have a set of clear pictures showing the whole machine and details that I could include in the Archive?
My best wishes,
Tony.