Silver King chain adjuster thread size?

[Cycleologist]

I have a possible 1934 Silver King / Hawthorne frame, SN 1673. A 1/4 x 20 in bolt fits in the rear of the chain adjuster threads approx. 1 inch but not in the front. It appears that a NON mechanic worked on the frame. Can someone tell me what the thread size should be so I can try to repair it.
Thanks for your help

 

[TR6SC]

1/4-28

 

[Cycleologist]

Thanks. And thanks for pix. It also gave the length.