Vintage Martin color

Looking at pics of various instruments, I have seen some variation in color of vintage Martins. Most are a medium brown color, with many looking to have a natural finish. There are some that seem to be much darker, like the color of dark chocolate. Did Martin make instruments with different color or stain, or is this due to something else over the years, perhaps someone treating it with something?

Most Martin ukes are made of mahogany which is a quite pale wood and therefore usually gets stained to make it more attractive. I would think that the actual stain used was quite variable from one batch to another before automated production methods were used.

I bet there was a bit of natural variation in the wood to begin with, then add the finish, which could darken up via UV light exposure, also sweat, body oils, smoke etc.

The mahogany they used did very in hue, I found that when the finish was removed it took some experimentation to come up with the proper stain that seemed to work on the different years and styles.
I would make up a batch that was good for at least 6 rescues. I'd have to start over when that ran out as I had no way to measure the combination.