Looks like this Oregon form allows businesses/dealers to claim tax exemption for items to be resold.
However, it appears that you must be a registered business in Oregon (see box for "Oregon Business Registry number").

Of course, dealer tax exemption is only for goods to be resold, not purchased and kept for personal use (collection).

http://www.oregon.gov/DOR/forms/FormsPubs/or-business-registry-resale-cert_800-002.pdf