Re: Selmer Mark VI Tenor Sax
First, I'm sorry to hear about your neck getting lost. I'm sure you've tried everything. But if you haven't, please make sure to track down the owner of the store and ask where your neck is. If you dropped it off when they were open and came back in a reasonable time frame and they were then out of business, the neck could not have gone far. If the assets were seized by a bank, you're repair claim ticket should be enough to prove the neck is yours. I would not give up on this without a serious fight. It would be criminal for either the business owners or the seizing bank to have sold your neck. If it just got thrown out, then you may be out of luck except for a small claims suit. An original Mark VI tenor neck in the 166xxx vintage should be worth about $700-$1000 in good condition.
As for selling, you could try selling it without the neck, but you'd alienate a large buying population. Most people interested in buying your horn without a neck would be resellers not end-buyers. However, considering the cost of buying an original Mark VI tenor neck, it may be a wash at the end of the day. For example, you may get $4000 "as is" and $5000 with a Mark VI neck. But you'll have to spend about $1000 to get a Mark VI tenor neck. So, is it really worth it???
You may want to consider a new copper Selmer Serie III tenor neck. They work extremely well on a Mark VI and it would at least be staying with the correct brand. You can find them for sale at Saxquest for $450. This would keep your end-buyer interest. However, to a reseller, it would not add much value.
If you decide to look for a Mark VI tenor neck, any Mark VI tenor neck that has not been altered severely can be made to work on your horn. You may have to have the neck tenon slightly adjusted to make for a perfect fit with your horn's neck reciever. But that can be done at any competent shop. Be careful with eBay as many times faults are not pointed out. Look for the neck being bent or dents or damage repairs. You never really know how a neck will respond with a horn until you try it. Some are good and others are so-so. But it will certainly add value to your sax to have a Mark VI neck with it.
Also, as for value, you're probably not going to get $7000 for a 166xxx Mark VI tenor in today's market unless its original lacquer and in mint to near mint condition and fully set up and adjusted. However, the $5k price range is reasonable given its in decent original lacquer.
Best of Luck!!