1. If you Google 1805 Lionel auction results, you will find a couple of previous auctions for your 1805.
2. Prices are declining, for example, I paid $800 for a nice complete 2527 military outfit approximately six years ago. Two months ago, I purchased a second 2527 in better condition for $525.
3. As Lionelman stated, reproductions abound, examine those items carefully.
4. Are you going to keep it, run it, or display it? Are you going to resell?
5. What is the size of this collection?
6. The final price for any 1805 depends upon multiple seller and buyer factors.
7. Good Luck!