I have an old Trefz Spinet Upright and the SN is 10887. Can you tell me how old it is.

Contact a vendor or vendors who may be able to provide a copy of the manual:

https://www.ebay.ie/itm/SWAN-COMPACT-TEASMADE-ELECTRIC-TEA-MAKER-VINTAGE-RETRO-APPLIANCE-TEAS-MADE/113898267601?hash=item1a84dda3d1:g:lvYAAOSwqb5dh1x~


https://www.ebay.co.uk/p/Swan-Teasmade-Compact-Model-No-10887-off-White-Retro-Vintage-Teapot-Alarm-Clock/1723345416

M4(105) Sherman USA std SN 58235 RN 30105007403
403 Should have RN 30104750. This M4 is stored in Georgia.
M4 Sherman Production Designation Manufacturers Total Date M4A3 Ford Motor Company 1,690 June 1942 - September 1943

(1905)!! Please Read On How To Tell How Old Your Piano Is !! I Learned This From Grandma !!
Piano serial numbers usually have five to seven digits, but may have fewer or more, depending on the manufacturer and age of your piano. Serial numbers may also include a letter as well.
Here are the TOP FIVE places to locate the serial number of your spinet, console, or upright piano:
Serial number locations are found:
1) On the piano's cast iron plate. After lifting up the lid, look along the top front area of the plate. The serial number may be to the right or the left, or in the middle.

2) Under the opened lid on the ledge, stamped on a little plaque, to the right or to the left.

3) Stamped on the back of the piano; near the top of the wood frame.

4) Printed on one of the hammers, found on either end of the piano (newer or imported pianos).

5) Printed on one the keys - behind the nameboard, inside the piano (newer or imported pianos)

this site will help with your estimate
Baldwin Piano Prices and Value Upright Grand New Used

I hope this helps. I can tell you that pianos age like people. How old is your Baldwin? Baldwins also are not made anymore, but I don't think that makes them particularly prized. Alot depends on its condition. I do not know to what the serial # and style # refer. If by upright you mean not a spinet or console, this type is usually found relatively inexpensively (<$1,000), especially if it is not a player piano. I would suggest that you take several good pictures of it to a local piano store for an estimate.

Possibly upto 7 years old but call Fischer & Paykel with the serial number and they should be able to give you the day month and year of production, the only number i can find for customer services is : 08000 886 605

Baldwins from the 70s and 80s are a bit notorious for various mechanical (and tuning) problems. Most of them pianos were good, but they might have a few parts that were bad, so be aware that you'll need to tune it to sell it, and you may need to do some repair work.
Most prices are listed by model number, not serial number, so you'll need to figure out which model you have. I found a pricing guide, but I don't know how recent it is. There is contact information on the page that might help, though. Baldwin Piano Prices

Just visit a web site with the serial numbers listed. e.g.
http://www.bluebookofpianos.com/serial1.htm#CABLE-NELSON

get ahold of manufacturer (Goodman) give them model/sn and they will be able to tell you the year the unit was made.

the key "POWER" +"TV/AV",