That's good luck, mandotim!
Lin's recommendation seems to be the soundest of all, especially the "good home".

This reminds me of the Spanish guitar, about 100 years old, I got from a good friend of my grandmother, because she preferred the piano, and the balalaika from a carpenter who lost three fingers in a saw. Thea both were glad that their instruments found a new home where they are appreciated and played.

The Carena 2 isn't produced anymore by Hohner (the best German firm); their 120 bass instruments are ranging now from EUR 1200,- on (that's a fistful of dollars more)to several thousands more. Considering the age of the instrument $ 500,- should be a fair price.

My accordion days with selling old ones and buying new ones for my musical training are over since 50 years, so I can't give you more contemporary informations.

Grab it, play and enjoy!