A mysterious no name 4G-4E lens

[kievuser]

Hi lens fans,

I picked up this mysterious lens a couple of days ago at a used cameras shop in Beijing. I thought it was another Chinese enlarging lenses, but it is different from my other ones that it could stop down only to F11 while most my enlarging lens stop down at least to F16, or F22 and its aperture ring turns the opposite way. I openned it to check the design and found that it is a 4 group , 4 elements lens.I believe this is the first one of this type in my lens collection! The lens has no inscriptions for focul length, no brand name, no s/n, etc, so it was not intended for sale.It appears well made and finished, and seems quite rare.
So what could be its original use? It has a M39 mount and can be used as an enlarging lens. Its focul length is about 75mm-80mm compared with my other 80mm F5,6 enlarging lens. Its coating colour is also a little different.

I will appreciate your input.