Post a bigger picture of the whole install. Can you tell if it's a thinset, or mudbed install? That looks 80's to me, not 60's.

I agree we need to see the whole space but to me those are better than many tiles we see . I think it does not matter if they are original if you love them work with them if you don't plan on replacing when you can.ON my monitor the flower looks navy blue so why not a navy blue floor .

I agree, looks like the '80s. '60s probably would have been simple glazed 4" squares in a color that we wouldn't find attractive anymore. :-) If you want to get back to a MCM look, search the pictures on Houzz for what people are doing for updated MCM. The tilework in the bathrooms shown below isn't what would have been done in the '60s, but the vanities are in the style. Unless you have an example of high end, landmark mid-century architecture I don't think you need to reproduce what was there orginally. A gray slate look floor with a walnut vanity would be close to authentic and go with a variety of tile.

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The medium brown grout color is 1980's or early 1990's.

Our home was built in 1980 and had tile work that resembles yours...not the same color, but size, grout color and width, and decorative accents are similar. The entire development had variations on this type of tile on the floors, and kitchen counters and bathroom shower and tub surrounds, so I agree with others...1980s. We lived with it for 18 years before remodeling. Yours is more attractive than ours was!