First off, Hohner Verdi's are the workhorses of the Hohner line along with the Tango and a couple other similar models. When new, they were affordable, reliable and sounded pretty good. Production of the Verdi line started in 1935, but a Verdi III ran from 1953 to 1961 with brief releases of the Verdi line in 1973 and 1987. Yours looks to be from the 1953-1961 years range.
That said... I have an acquaintance that recently bought a porsche cayenne turbo with the top specs over an internet auction. It looked beautiful and for a bargain price of $12,000 he snapped it up this supposed $35,000 car.
As soon as he started it, the engine made knocking noises, which turned out to be wear in the cylinder walls due to improper maintenance and cost to repair it was over $15,000 in parts and likely another $20,000 in labor!
Value of his car? Well a big negative $5000+ on a GOOD day... so basically... zero, though he *could* pay someone to take it from him if he paid enough... lol
Like cars, accordions can look good outside, but as I repeat (for likely the 100th time... lol), the value of any accordion is on the inside, not the outside. They all look nice given a 5 minute wipe down with a paper towel, but what is the condition INSIDE?
Accordions hate humidity, hate large temperature changes, hate not being used regularly and hate not having regular maintenance.
A nice looking accordion with issues inside can quickly exceed it's market value (and let's be honest, there are very limited levels of accordions who's value has more than 3 zeros on the end of it out there today, the vast majority are low end or student models, though to be fair, there are accordions out there that have a 5-digit price and value where the first digit is not 1-2-3-4 or even 5! Unfortunately, this is not one of THOSE accordions).
This accordion if in PERFECT LIKE NEW condition would be worth between $500-$700, but a valve replacement for both sides, tuning and rewaxing will easily cost you double that, and thats with a lower end budget oriented repair person. A knowledgeable professional will ask triple that without batting an eye.