Thank you for your patience.
From this maker’s records the serial number you have given shows that your piano was built in 1948, so it is in the region of 68 years old. Knabe is one of the old long established American Companies and has a good reputation for making quality pianos.
Generally Pianos have a limited life span of around 60 years mainly due to the wear during use and natural deterioration of the mechanical parts over time, such as the action, the strings, the soundboard, the tuning pins, the pin block, etc. The life of these instruments can often be extended by careful regular, usually at least annually, maintenance/tuning/repairs and some restoration over the years or a total re-build/restoration of the major mechanical components. Added to this is the consideration of the type of environment in which they are kept and the amount and type of usage. Thus one of the overriding factors in any appraisal valuation is the age and condition of the internal mechanics. I will base this appraisal on the fact that, save for regular tunings and any maintenance associated with tunings, the internal mechanics are essentially as originally built.
At 39 inches high it is classed as a Spinet piano. It is quite a compact size and thus has a small soundboard which can restrict the volume and quality of sound produced. This size of piano is generally no longer made as it has been superseded by larger better sound producing uprights.
Therefore based on the information I have and that which you have provided I believe this Knabe Spinet Piano now has a value in the $500 to $700 range for a private sale. I am sorry that it is not better news. Unfortunately there are now a good many of these smaller uprights for sale and thus the prices can be depressed. As far as selling it is concerned I suggest that you try advertising in your local newspapers or similar journals initially – they often have free advertising spaces – and if that does not bring any interest try craigslist.com which is also free.
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If you are disappointed in the value given ‘please do not shoot the messenger’, I can only give you a value based on the current markets and a reflection of the same or very similar sales. Owners of musical instruments often have a very sincerely ***** ***** that their ‘pride and joy’ is particularly valuable and sometimes it is, but musical instruments unfortunately generally depreciate with age and/or changes in technology. Many thanks and if you need any more help or explanations on the value I have given please contact me before you complete the rating.