We used to get all sorts of WW 2 junk in Christmas snowmen, remember them? About a foot high, covered in cotton wool?
Fold flat gas or sand eye shields, small sellotape sized rolls of window wound round an aluminium core, and Zorro type metal masks.
The mask was my favourite, Matt black, backed with a soft rubber compound, cruciform crosses over the eyes. Perfect vision though tiny slits. I imagine they were anti-spaulling devices for tank crews. Don't know if that was true.
Ps, the picture is very similar to the I-band filaments bbc we chucked out the Shack in the 80s. The stuff I described above was the real deal - tinsel or rope for metric band. While 2-3 foot sections would have worked I think long strings would twist and snake giving multiple returns at the right wave length.