Ebay!

That has eliminated perhaps 95% of your potential market - I'm sure there would be plenty of German collectors who might be interested in those items.

Your choices are narrowed to a 2nd hand dealer who will only give you half of what the items are worth because he needs to make a dollar (or euro) as well, an auction house who will take considerable fees for selling, approaching a local Marklin club or perhaps offering the items for sale on a forum such as this one. There are certain conditions to be met before offering items for sale on this forum which can be read here:- https://www.marklin-user...-forum---Read-this-first

The other option is offering them on a Facebook group, but then I guess you'll tell me you don't do Facebook.

Oh dear, between ebay and facebook, you have missed out on your easiest markets ot sell.

However as you are in Germany there are a couple of auction houses that regularly deal in Marklin. I don't have contact info for them, but I know at least one person on this forum that does. I'll leave it to them to provide you with relevant contact information.

New members can't really post items for sale in the forum, especially when they only have 3 posts and all of them are in a topic related to selling those items.
That said, welcome to the forum...

https://meine-flohmarkt-...eugmarkt-boerse_0-9.html

Try this list to find places where you may be able to sell your models

You can also offer the models to shops like Schweickhardt or other who sell used models. You will probably not get full value if selling to somebody whose intent is to buy low and resell for a profit. That is why eBay is a good idea because you can reach the collector/buyer directly.

Regards

Mike C