I'm selling most of my pens but need some info please.

[DavidDecorator]

One of the pens I'm going to put on ebay is a 1920's White/cream marbled Ontoto Delarue on cleansing it and resacking etc I discovered that it is fitted with a Wahl Eversharp nib. I think this makes it pretty unique so I'm wondering how much it could be worth. Apart from the brass clip and lever
being a bit tartarnished due to age I suppose it seems to be in excellent condition.

[piscov]

Put some pictures here and you may have someone to give you some help, but a pen with a incorrect nib always devalues, unless it has a very rare nib installed and the nib itself is more valuable that the pen.

[tandaina]

Yup, Piscov is right. Someone might buy the pen for the nib value if it is a very rare nib, but usually that just means Frankenpen and will be skipped by most collectors. Wahl nibs are a dime a dozen out there. (Onoto nibs are much less available in my experience.) Unless it is a flexible Wahl adjustable nib it is likely not terribly sought after. Expect to get less than the pen would be worth with its proper nib. I buy such pens ONLY if the nib is something I am looking for specifically and then I'm really only going to pay for the nib in most cases.