It is while inquiring about this lens that I learned that Pentacon chose Meyer's lenses and not Carl Zeiss ones to become its standard lenses!
Pentacon 1.8 / 50mm
I recently discovered that there were two possible 1.8/50mm provided with the Prakticas. On the one side, the Oreston from Meyer Optik Görlitz, on the other, the Pancolar from Carl Zeiss Jena. And Pentacon 1.8/50, and following Prakticars are not the descendants of Zeiss's Pancolar, but of Meyer's Oreston!
Meyer Optik Oreston 1.8/50mm, on the Praktica LLC bought in a secondhand fair august 14th, 2011.
Pentacon Auto 1.8/50mm.
The same lens afterwards called Pentacon.
Tests: Please note that these tests were made with the means at hand, not in a "scientific" way. See here.
Less good than Helios44. Like for it you should diaphragm to f: 8 or 11 for a uniform result over the entire field.
Aus Jena Pancolar 1.8 / 50mm, on the Praktica LTL bought by Christophe in a secondhand fair in october 2009.
Old version. Not multi-layer coated.
MC Pancolar 1.8/50mm, given by a customer.
And newer, multicoated.