Vintage helmets have become a "Thing" some people are relining them and using them!
I personally would never use one on the road. As others have noted, One should NOT trade in used helmets with any thought of using them on the road or track.
Many experts also say they have an expiration on them as well,, old helmets dont hold up.
However there is a market for them. Some want them for shop or mancave decorations or your hipster bar or clothing shop. (Post LOTS of photos on Instagram to your followers)
Some use them as art projects. Our annual ONE Moto show here in Portland has a very competitive contest for art work called "21 Helmets" and some pretty cool stuff being done.
See:
http://the1moto.com/21-helmets/On our old farm, and my shop & business the driveway leading to the shop bordered on my cow pasture and I had an old helmet on top of each fence post and a few I stuffed halloween masks with expanding foam and put the helmet over the mask and fence post. Creeped out some people, but others would bring friends out just to see them and take pictures. This was before social media,, I suppose It could have gone viral had I kept them.
I DO have Maggie Neato, and she is a full sized store mannequin, I use her in my stalls and booths for events where I do promotion work, She has a Norton leather jacket with large logos, Parachute pants,A very worn leather belt with a Norton brass buckle and it came from a famous leather shop called "Langlitz leathers" and held up the shop managers pants for 3 decades,, A Norton Silk scarf, and currently has neon pink wig, a Pudding bowl cafe helmet and googles. Quite the cafe racer lass and stylish.
I have some vintage helmets from the 60s and 1970s, And thinking of selling them, I had planned to use as decorations (Art pieces) but debating on trying to get some Hipster with loads of disposable income who wants them and will pay crazy hipster prices. I have some crazy bubble face shields as well. One of these helmets was worn once and I have the receipt from 1973.
My friend Lee came back to the US in 73 and wanted a BSA Twin 500. Was not aware of BSA's woes and couldnt find any dealers with a new 500 twin in stock, settled for a B50 badged as a Triumph, and they wouldnt let him leave unless he bought a helmet as well. *I THINK the Oregon helmet law had just passed at that time, * But he didnt like helmets, so wore it once. I have it.
My Friend Sir Eddy had an old Portland meadows horse Jockey helmet and very similar to a Pudding bowl cafe helmet. It had leather sides and strap. Eddy wore it for years. He hated that it made his head sweat so put it on his milling machine and drilled a pattern of small holes down the center for cooling which worked well.
However it didnt protect his noggin well,, and when he had his crash (Deer ran across the road, leapt up and knocked him off his steed, It killed him, but paramedics revived him. He died on the way to the hospital and was revived again,,, So, I saw it post crash soaked in blood.) So, I dont recomend doing that sort of thing.
I personally bounced on my own noggin and thankful I was wearing a helmet, Dont cheap out, Dain Bramage is a terrible thing.
See:
https://www.youtube.com/watch?v=tI4c21w77JU (I resemble this,,,, Dain bramage)