Hi,My name is***** have been dealing in and appraising Musical Instruments for over 40 years, and I can help you with this. What model is your bassoon? Is it a 5071?
Based on your description and my research, your Bassoon is circa 1950s. This would sell for $5000-7000 at auction, and insurance replacement value is $10,0000. A new Bassoon similar to yours would list for $20k and sell for $16k.
$16-20k is for New not used. You can buy used for $6500. A music store may sell this for $10k, hence insurance replacement value is $10k. You said Schreiber & Sohne is it W, Schreiber? You said
"My wife doesn't recall that she received any paperwork when she purchased it used from Schmitt music back @ 1988" Im confused New or Used please confirm? If it is from the 1980s it should be W. Schreiber?
There is really no serial number info available. Insurance replacement value is $10,000 for your bassoon. Here are current new models
This is in £ figure about 35% more for US Dollar.