How much is this old Nikkor lens worth?

I have a Nikkor 28mm 1:2.8 manual lens circa 1981.
The front lens is scratched in a couple places.
I'm interested in selling this item, but I'm not sure how much it's worth?

The front element being scratched makes it worth much less than if it were pristine.

The 28 mm was popular because it was the widest angle lens at the time that could be used with an electronic flash without vignetting.

Since then the 24 mm, 20 mm and 14 mm lenses have become popular with 35 mm shooters as well as full frame dSLR users

My guess is that the lens is an AI-S type, so it can be used by professional level Nikon D3 and D4 dSLR cameras as well as the Nikon F4 and F5 cameras.

What is it worth?

Here is a link to such a lens, but you will have to back out the cost of regrinding or replacing the front element of the lens. For that, you will have to call Nikon and get an estimate

http://www.keh.com/camera/Nikon-Manual-Focus-Fixed-Focal-Length-Lenses/1/sku-NK06010200045N?r=FE

With the front element damaged like that I would guess about 100 to 150 dollar. Having the front element repaired can be quite expensive

By doing a quick advanced search on eBay and looking at completed auctions prices ranged from £21.00 to £143.59 these were all perfect ones.

http://www.ebay.co.uk/...=1&_ipg=50

It's good way to find the current value of most anything.

As the lens is scratched you may not get any bids at all, photographers won't buy lenses with known faults, if you don't mention the scratches in your listing your customer will most likely return the lens to you as 'not fit for purpose' and Pay Pal will (eventually) refund the purchaser and debit your account.