What era is this suit?

[Rupert T. Firefly]

Some are pretty easy to recognize but I am having trouble on this one.
The only remarkable thing to it is that there is a notch on the back of the waistband.
Thank you for your help.

 

[Fastuni]

The narrow lapels suggest early 1960's. But they are either badly pressed or it was a mediocre alteration job (50's suit with broader lapels narrowed down).

 

[Guttersnipe]

What you have here is an early '60s suit in the "Ivy League" style that hits all the key points (three-buttons, no darts, natural shoulders, and it looks like the pants are flat front too). Those slightly rounded lapels, which are sometimes called "clover leaf" or "Shamrock" lapels, were in vogue from about 1959-1963.

 

[Baron Kurtz]

very Mad Men; classic early-middle 60s suit.

 

[Rupert T. Firefly]

It does need to be pressed.
The fabric is summer weight and there is no lining on the jacket in the back.
No pleats so good eye Guttersnipe.