Thank you Mike, Jim, Bruce, Andrew, and Don.
Yes, the stretchable thread was Uschi brand, very similar to EZ line, only much smaller diameters. Stated sizes taken from their respective websites:
EZ Line
Fine – .010″ (0.25mm)
Heavy – .020″ (0.5mm)
Uschi
Standard: 0,03mm
Fine: 0,02mm
Superfine: 0,01mm
I'm not totally sure Uschi has the measurements correcetly displayed, because they suggest to use their standard size for 1/32 aircraft. That would give you only .96mm real scale bracing wires - way too small! Even with the naked eye , I would only use their brand for 1/72 and smaller, and perhaps their standard size for 1/48 aerial wiring - even though the math says too small.
regards,
Jack
edit - took a look at the Uschi packaging, and here the measurements are expressed in inches. So included the corrected metric size:
Uschi
Standard: .005'' = 0.13mm
Fine: .003'' = 0.08mm
Superfine: .001'' = 0.03mm