Is this rosewood?  

I would -guess- yes.

Thank you Lief!

Lief was rosewood used more prolifically in Danish furniture in the 50's/60's or was it used across the board in furniture of that time? I assumed the chairs were Danish but one should never assume!

Rosewood was used more frequently in the mid to late 60s I would guess. And it was also used frequently in Norwegian pieces.
Basically you tend to see it more frequently in designs that were fighting against established designs for attention.
So, as an example, Wegner's designs never lacked for attention and many were executed in oak, or teak and oak, or all teak, but it is extraordinarily rare to find a Wegner design executed in rosewood.
And there are certainly corner cases and counter examples.

Thanks Leif! That makes sense, I had thought my chairs, due to their quality and the rosewood, were by a Danish designer. However no one in the know has identified them so I'm assuming they are as you say, someone fighting for sales and not a big designer. Did you happen to have a view on them?