I think the answer to your question is a resounding NO. There is NO SIMPLE WAY. If there were we would have all heard about it. There are so many variables that go into spur length.

According to the "Wildlife Techniques Manual" Published by the Wildlife Society, Kelly examined 3 age correlated vairables, spur length, beard length, and body weight. To find out what Kelly wrote about here is the info. Kelly, G - 1975. Indexes for aging eastern wild turkeys. page 205 to 209 in LK Halls (ed). Procededings 3rd national wild turkey symposium. Texas Chapter Wildlife Society, Austin 227 pages.

I would just call your wildlife technician and ask him or her. You'll probably find out that there is no real way. I always get a kick out of those bumpkins on TV that quickly glance at their bird's spurs and say "now thers a nice 3 yr old bird, aint that right bubba!" You might as well put your ear next to your dead bird's head and say 'he just told me he was 3 yrs old"

But what do i know, i only graduated from college in Wildlife Management, but didn't into a state wildlife job. Call your local person and use the spur length as a guidline.

My question is who really cares if it's a 2 yr old tom or a 4 yr old tom? It's not a jake!