Apart from the 500 holder are any of the other holders obsolete?
What of the 550 pack film holder?
I am thinking of getting a Polaroid back for my Graflex. I therefore want to be sure it is a 405 holder or 545.
How does one tell the 550 and 405 holders apart?
I don't want to end up with the wrong one.

Any idea which this one is?

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=7617702713&ru=http%3A%2F%2Fsearch.ebay.co.uk%3A80%2Fsearch%2Fsearch.dll%3Ffrom%3DR40%26satitle%3D7617702713%26fvi%3D1

A shame the image doesn't show the end of the holder because the end of the 550 holder is much thicker. I reckon this auction item is a 405 holder. What do you think?

Not really a good way to tell from the image, it looks like a 550, all of the 405 holders I have had have been blue inside and the 550's have been read, but really not a good enough picture to acertain...I know there have been others over the years, that polaroid made for different camera companies.

polaroid 550 http://cgi.ebay.com/Polaroid-550-4X5-Sheet-Film-Holder_W0QQitemZ7616231955QQcategoryZ11813QQrdZ1QQcmdZViewItem

It is a pity that one cannot attach images to these postings but the vendor of the item came up with some more images that lead me to suspect it may be a Polaroid 405.
The edge of the holder body has a 'lip' around it. Probably because as the pack film is smaller the holder is also and so to fit on a 4x5 camera back a little extra width is needed.