I think that this is an early Falcon SS derailleur, branded up for Columbia. It is slightly interesting in that it is an early example of an American manufacturer branding up a Taiwanese derailleur, rather than a Japanese  or European model (like Schwinn or Raleigh).

It’s plenty rusty.

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1. •Brand: Columbia, manufactured by Falcon
   

2. •Country: USA, manufactured in Taiwan
   

3. •Date of introduction: 1980?
   

4. •Date of this example: unknown
   

5. •Model no: unknown (hanger plate stamped ‘A04’)
   

6. •Weight: 301g including hanger plate
   

7. •Maximum cog: 28 teeth?
   

8. •Total capacity: 28 teeth?
   

9. •Pulley centre to centre: 54mm
   

10. •Index compatibility: friction
    

11. •Chain width: 3/32”
    

12. •Logic: top normal
    

13. •Pivots: two sprung pivots
    

14. •Material: steel
    

0093/C