I have come across this in other contexts where it simply means in essence "something that needs to be taken into account" but is not given an actual figure. I've seen it sued, for example, in cooking recipes, where it means "you'll need to remember to add salt and pepper, but we're not telling you the exact quantity"

In your context, I imagine they are including things in the list, but not actually assigning them any specific value — they just want the buyer to take into account the fact that all these extra items are included in the overall valuation, even if they are not actually being individually priced. It's just a more formal way of avoiding writing "€ 0" — which psychologically tends to make the reader think it isn't worth anything!

Perhaps you can add up all the figures to see if this makes sense?

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Note added at 8 hrs (2018-07-18 12:00:17 GMT)
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Yes, Asker, that does indeed seem to be along the same lines, doesn't it? It probably means the items are so old they have long since been depreciated and hence have no 'book' value — if this was originally a business, the figures used for the values might well be taken from the actual accounts, which would explain the distinction being made. And 'occasion' could well mean it had originally been bought second-hand, and so never had any book value in the first place, say (no original invoice from new)