Men's Suit Jacket without labels - help wanted

Hi there! I've come into possession of a load of ex-theatre clothing dating from 1920s to more modern. I don't know much about men's clothes though so I was hoping someone might have a rough date for this piece as the labels have been taken out at some point in its life

I've taken photos of every part I think will be useful, if any others are wanted, just let me know.

Thanks! V

 

Hello!
Is the back lining of the jacket full length or does it only cover the upper half of the back?
It would be helpful to have a photo of the entire interior of the jacket.

 

Full length lining. 3 pockets to right side (as pictured), middle one is quite small. 1 pocket to left.

 

Thank you! I had it pegged around 70s as my dad had something similar in his closet.

There are signs of a label having been attached to the lining. Unfortunately, no other labels hidden in the pockets.

 

Update: Noticed the buttons had roman numerals on them. A UN type logo (globe with wreath) with an eagle on top then the year underneath. Roman numerals say 1979.