Thrones, what are they ingame?
I tried looking for info online, but to no avail sadly.
Are they gold coins of various sizes, little chips, maybe just data on a creditcard?

Thanks in advance

Due to the technological status of the Imperium I would assume that thrones are coins with a picture of the Emperor and the Golden Throne on one side and some important guy or gal on the other, depending on where its minted. I'd also assume that there are many different versions and looks of Thrones and but that the system used in the game is a generic for what value a things has. So for example something that costs 15 Thrones may in fact be paid in 8 Malfian silver Thrones and 1 Scintallian gold Throne or 3 Scintallian gold Thrones and 1 Sepheris Secundian electrum Throne.

The book actually goes into this for a little bit, but it really is just to say that a unified currency is effectively impossible in the Imperium. It varies by world and by culture. The prices in the book are generally meant to reflect "standard" imperial society, most likely on either a hive or "imperial" world. Credit systems theoretically would exist (but I'd hate to see the bookeeping that goes into that). I imagine they do have some sort of coinage, but really, the imperial war machine being what it is, I see no reason they wouldn't use paper money (as those metals could be better used elsewhere).

Really, its whatever you want it to be is the actual answer. If you can't decide, flip a coin.

Tbh it's not something I've ever really worried about though I have had a few variations depending on the tech of the world. In high-tech areas there's the credit chit which works like a debit card and in lower areas non-military grade metals are used.

I really should put more thoguuht into this to increase imemrsion. I'll come back once I've had a thinksee

This discussion over on Dark Reign 4 years ago…

http://darkreign40k.com/drjoomla/forum/index.php?topic=533.msg8637#msg8637

In my campaign, I've borrowed the concept of 'credit wands' from some Dan Abnett books: pencil-sized rods with data chips on the end that can be read by standard dataports. As KommissarK said, true credit (with interest and whatnot) would be a book-keeping nightmare, so I just treat then as 'debit cards' that access pre-established bank accounts. -And not every business accepts them, of course- seedier establishments operate on hard currency (or local equivelant, such as some kind of paper scrip issued by local employers) only.

The book says its a generic representative for the thousands (millions?) of currencies used throughout the Imperium. Per the book, I got the impression that many of the most advanced planets and systems use relatively advanced currencies (some sort of electronic/credit type system) whereas more remote planets and low-technology worlds (feudal societies or whatever) have their own coins.

When its come up in my games,we've used it as an electronic/money card type system. IE credit exists as do pre-paid cards. Its really however you want to run it. If you had a whole campaign set on a feudal world thrones might represent the local gold supply.

As has been stated throughout the thread, in the DHCR Thrones are stated as being the general name covering the wide varieties of currencies used throughout the Imperium, from literal coins and paper bills to virtual money on a credit slip to even used gun casings in some places such as Gunmetal City on Scintilla.