Hi Dirk; welcome to the board! We have a few other members from Belgium as well. A Series I from any year is a wonderful instrument. The older it is, the more susceptible it might be to RF noise. This varies depending on location and the particular instrument; but most folks don't find it to be a problem. If a bass does have noise, it can be sent to the Alembic shop for an upgrade; but it is not inexpensive. Generally, Alembics are a little rarer in Europe than in the US, and prices are thus higher. I don't keep up with European prices, but generally in the US an '80 with Koa top and back should be between $3,000 and $3,500 USD, maybe more, with the power supply and form fitting hard case. The mint condition could add more. If it's missing the power supply and case, then factor that into the price. I have an '86 S1, and it is an absolutely wonderful instrument. An '80 in mint condition; I would tend to say go for it.