A nice set of vintage 5" linking rings. 
 
The manufacturer and year produced is unknown
 
Includes:
 
3x One Ring
3x Two Linked Rings
1x Three Linked Rings
 
CONDITION NOTES:  Overall in good condition. They could use a light polishing, and I am not certain whether the additional two sets of linked rings are original to this set or from another example by the same (unknown) manufacturer. Some of the welds are slightly rough but could be easily touched up if you’re handy. The box is in excellent condition. As noted, the manufacturer and decade of production are unknown.