The vast majority of specimens held at the Carnegie Museum were prepared by staff employed at the museum during the 115 years the museum has been in operation. There are a very few specimens that were donated or traded over the years done by other taxidermists. For example, we have a Grizzly Bear mounted by James Lippett Clark - but I am not sure if it was collected by a local and mounted for us by Clark, or what the situation was. That specimen is not on exhibit.
The crocodiles you mention were collected both with a Bow and Arrow at great risk to the hunter, a Pittsburgh businessman. Because certain companies in the United States advertise through certain venues, these companies often get business from big game hunters. The largest company is probably Animal Artistry in Reno Nevada which has built up a large clientele of hunters through the Safari Club Internation which meets in Reno on a regular basis.
This Taxidermy mount was done by taxidermists at Animal Artistry and the hunter later donated the specimen to the Carnegie Museum. You can even see a photo of the piece still on the AA website at
http://www.animalartistry.com/pb/af_ls/20_af_ls.phpIf anyone reading this post does know who the actual taxidermist that did this piece, please list it here.
The Nile Crocodile mounts were donated probably 8-10 years ago or so when they were first put on exhibit. They were off exhibit for a while during the building of the new dinosaur hall.