As far as I can tell in Aperture, unless the master is offline or missing, I can't do anything like that.
If a master/original of an image is referenced, you can show the original file with
File > Show in Finder
but only if the original is not offline or missing.
You can check the file status of your original/master image files using smart searches or smart albums. Add a rule to the smart settings HUD "File Status is" - the images that are referencing the iPhoto library should have the file stautus "referenced" and you should see their masters with "Show in Finder".
What is your Aperture version? If you had Aperture 3.3.2 and iPhoto 9.3.2, you simply could open your Aperture Library in iPhoto and then use iPhoto's show command to show your managed masters, but since your signature is MacOS X 10.6.8 you probably have an earlier Aperture version.
Ok, both post were very helpful. But let me explain a little better what I have. I am using Aperture 3.2.4 on 10.6.8. I will be updating later this week.
I have some 600 plus pictures that are managed. Some 6000 that are referenced. I had already created a smart album like LeonieDF suggested. I called it manaded originals. It showed some 700 images. I found that some of them were from iPhoto. I expect I had exported them from iPhoto to a folder and then imported them into Aperture as managed, so that I couid fine tune them for a DVD.
Turns out I already had a smart album that looked for managed masters. But this album is populated with different images. I'll start another post for that issue later.
Now for the iPhoto export photos, I want to only have them in iPhoto, but before I delete them from Aperture I want to be certain they are not going to be gone from both iPhoto and Aperture.
I did a quick test and it seems as though the images are duplicated. One in each Library. There is a copy in iPhoto for sure. I did a show file in there and I can see it. Aperture...not so sure.
Can I be certain that if an image is in the smart album with the file status set to managed, then it has a copy in the Aperture Library somewhere. I think that is what I am getting from the responses from Lionie and Frank.
Yes if you search for File Status -> Managed
Then the originals of the images found are in the Aperture library Masters folder.
However it is always a good idea when deleting images to do it in multiple steps. That is delete the originals from Aperture (this will place them in the Aperture trash) and then make sure the copies are still in iPhoto. Then empty the Aperture trash placing the images in the system trash and check iPhoto again. If you still see the images in iPhoto and checking the location of the original in iPhoto still shows thme to be in the same place as they have benn and not in the system trash file it would be safe to empty the system trash.