[Update below]

Premeire Props is having their Hollywood Auction Extravaganza XIV on June 21-22 in California. Included in this auction are quite a few listings labeled as from the first two Hobbit Films and the three Lord of the Rings movies. A linked list of these items is included below if you are interested.

It is important to keep in mind that provenance and authenticity are of absolute importance when collecting movie props. Premiere Props offers certificates of authenticity for any items that they sell through their website (see their terms here) but those same terms do not generally apply to their weekly auctions such as this one, where items are typically consigned by other sellers. For the live auction items, each item description details the provenance and authenticity guarantees that each item comes with. For example, here is an item from the X-Men films, where the item description states "actual hero screen used claws", "These are the hero rubber versions worn by Jackman", "The blades come with a Letter of Provenience from producer Lauren Shuler Donner", and "This item also comes with a Movie Props DNA", which is a system of authenticity that Premiere Props uses to authenticate items even after they are sold.

Now, if you read all of the below item descriptions, you will note that not once is it mentioned that these are screen used, none of the items comes with a certificate of authenticity, and no provenance at all is mentioned for any of these listings. Bidder and buyer beware!!! It is certainly possible that some, many or all of these are legitimate props, but as a buyer you will be very hard pressed indeed to document this for insurance purposes or later if you should want to sell them again.

[Update]I just now received this email in response to my queries to them:
All come from a guy who works on the props in these films. Premiere Props will provide a COA.
So the provenance for these items is "a guy". The Certificate of Authenticity is nice, though! [End Update]

Premiere Props has been documented as having some questionable practices in the past, primarily via the Original Prop Blog - for example, knowingly trying to sell a fake prop: "So, in short… Premiere Props listed a fake prop for sale as authentic… was subsequently told that it was fake… they left it up for sale anyway, and then changed it to an authentic fake, with a $200 start price… a price which was realized at auction with a single bid, yet the item was not sold?" And

The Lord of the Rings
392: Lord of the Rings Production Practice Sword Movie Prop
393: Lord of the Rings Return of the King Cup Movie Props
394: Lord of the Rings Two Towers Cup Move Props
396: Lord of the Rings Two Towers Necklace Prop
397: Lord of the Rings Return of the King Flail Weapon Prop
398: Lord of the Rings Fellowship of the Ring Necklace Prop
399: Lord of the Rings Fellowship of the Ring Rams Horn Prop
446: Lord of the Rings Two Towers Elephant Riders Sword Prop
536: Lord of the Rings Fellowship Practice Sword
537: Lord of the Rings Production Practice Sword Prop
717: The Hobbit Desolation of Smaug Dwarf Pants Costume
718: The Hobbit An Unexpected Journey Deer Hoof Dagger
719: The Hobbit The Desolation of Smaug Cup Prop
720: The Hobbit The Desolation of Smaug Cup Prop
721: The Hobbit The Desolation of Smaug Village Box Prop