Vintage folding opera glasses / binoculars. Super compact rare set of lenses

Superb design of glasses that fold down very small 

closed size in CM 6 x 3 x 2 

extended measurements are 

front lenses 12cm across

rear lenses 8cm across 

length 10cm

with the back viewers folding up and slipping inside the middle block, the front lenses fold 

back and held there by a clip on the rear lenses.

They function properly but they do have a fair bit of wear to them, though it is all superficial were the chrome has worn off and there are some small marks on the lenses. They must have been used a fair bit.

They also come with their original case, though as you can see in the last picture that it has pretty much disintegrated 

A super adition to any collection

I have not seen another pair like this, nor can I find anything similar