I recently purchased what was described as blue marble 58; I already have several, but the price was very good and I'm a sucker for these pens.

Upon receipt, I see that the color is much darker than any other blue marble I have seen; actually, it doesn't look blue at all. The color is uniform and the pen is clean so I don't think it is post-prodution discoloration.

It is an early 58, 2-line imprint:
The Conway Stewart
No. 58

Could this be plum marble (I've never seen that color); is it a purple so dark it could appear marbled charcoal-grey/black in some light? Or, is plum marble more toward the red end of plum?

Thanks for any help you may be able to offer.

Plum is definitely a very deep purple, it couldn't by any stretch be mistaken for blue and I don't think it featured in the 58 series. However, I have in the past owned at least two shades of blue marble 58s, one darker than the other. Rather than being a different colour completely I think it is probably just a variation in the batches of materials used.

If you're after a rare 58 colour variant I think you'll have to wait for another silver herringbone to turn up! Probably the next rarest after the silver herringbone would be the blue candy stripe, followed (maybe surprisingly) by the green marble! All the other colours seem quite widely available and (silver herringbone apart) I have owned one of each in the past, they make a great group to have.

Andy