The 450SE is a niche bike, Terry style configuration. You will need to be a very small rider for this style bike. Terry style bikes are hard to find, so depending on how hard you want to look/how much time you are willing to spend looking, I would adjust my offer accordingly.
Without detailed, quality pictures, really not feasible to give an accurate value. But if you really like the bike, and the price is within your budget, go for it.
Original tires is not really a plus, that means the tires are 25 years old. So the bike has set idle for 25 years. Will need thorough maintenance, probably new tires, tubes, cables, housings, grease. Depending who does the work, the cost of such maintenance could be minimal (do it yourself) to significant (taken to a bike shop). The good news on a bike that has been idle is that the cosmetics: paint and decals, are usually quite good, DEPENDING on how the bike has been stored. Make sure seat post and handlebar stem move freely (are not stuck).
Google Terry bicycles and you will find endless information about them. Note that Terrys usually command a hefty premium above the similar competitor bikes, as the Terrys have a big following (I have a Terry myself in the queue).
Last edited by wrk101; 02-27-11 at 08:16 PM.