Sohmer was a N.Y. company and was one of the more well-known American piano companies for quite a while. They were in business until the late 1980's when they were bought and sold to a few other companies. Sohmer pianos are no longer made, though the name might be used on other Asian built pianos.
A 5' baby grand is also called a "petite" baby grand or apartment grand. That just means they are the most compact baby grands on the market and work well in small spaces. The bass note response is generally a bit weaker on these smaller baby grands just due to length of string.
Since your piano is over 50 years old, there is a significant amount of value depreciation to consider. All pianos lose value as they age, due to the natural decline in both mechanical and cosmetic condition. I think, if priced right, this could be a quick seller on the used market (if that is your intent).
Based on the above factors and considering the used market and your description, I would recommend a selling range today of approximately $2,900-$3,700 in a private sale. Should you want to sell to a dealer or use a third party, you would likely only receive half of that value, since they would have to make a profit as well. I hope this helps and wish you the best!
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