Hello, I bought a bike from a person who said that it was a 1978 bike. I'm in doubt of which brand, has the lugged different from the others, it is very long and sharp. I've found some similar ones, but I do not really know which one it is. Some photos attached.

The serial number is: 76L94508 or 6L94508 (I believe that in the beginning may be a risk in place of 7)