Help dating top with a tag without a brand

[Racheljane]

I think this shirt may be from the mid 70's considering there is a style number and also because it is made in the USA. The tag just states washing instructions, style #, size, material, and that it was made in the usa. There is also no tag on the side seam! Has anyone ever found something with a similar tag? The cotton/polyester blend is throwing me off with dating as well.
Thanks in advance!

 

[Metro Retro Vintage]

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[poppysvintageclothing]

It does looks 70s to me. I have to say that I don't quite understand what is going on the side where your hand is, as the other side is plain.