I found this interesting (pdf) article by Christian Deydier who is one of the leading capacities on archaic bronze. It also briefly cover fake archaic bronze.

deydier.com/livres/iaba/Livre%20EN.pdf

A couple of quotes from the article:

"The latest fakes

In the past ten years, a great quantity of fakes has flooded the market. Coming mostly from Taiwan and mainland China, they are often of the highest quality, some reaching such a level of technical perfection that they completely fool many collectors and dealers. Genuine specialists are, fortunately, still able to detect them since they are often too heavy, their artificial patina can be detached from their surfaces rather easily, their inscriptions may not paleographically match the authentic writing of the period from which the object is supposed to date and/or may not be cast deeply enough, and especially because no corrosion can be detected actually coming from inside the object’s metal, since the false patina, such as there is, has merely been applied artificially to the vessel’s surface. No matter how skillful the copier, a true specialist will be able to see through the hoax, since for him or her the copy always lacks ‘life’, the vital energy that only a genuine antiquity possesses. The ability to sense this ‘vital energy’ is essential for anyone attempting to make an appraisal."

"Methods of detecting fake patina

Whatever the method employed by the artisans, all of these artificial patinas can be detected by an experienced person. Most of these artificial patinas are unable to resist a quick test carried out with a piece of cotton soaked in alcohol, acetone, or any other nitrogenous product. It is also possible for an experienced person with a sharp eye and armed with a magnifying glass to detect the hand of the forger in such patina."

Another quote:

"Fake Patinas

The artificial patinas applied to bronze reproductions are produced using the following materials and techniques:

■ Acids The earliest method used, and the most widely-used and easy, is soaking the bronze object in chlorohydric acid. A second related technique consists of soaking the vessel in a mixture of acid, lime, salt and colours. The object is subsequently buried to a depth of about a meter for a period of from three to four years. That allows a chemical reaction to take place, which creates a patina which is, in many ways, very similar to that on an authentic archaic bronze vessel. A third method is the use of a mixture of sulfuric acid and ammonia. After being kept in a very humid place for from three to five days, the emerged vessel will be covered by a green patina, which is difficult to remove. The famous fake-maker Wang Deshan 王德山 made extensive use of this method at the beginning of the last century."

So this mean there is at least one artificial (green) patina which is difficult to remove and can be mistaken for genuine patina?

One more quote:

"As mentioned above, a careful inspection of the patination of a vessel can play an essential, determining role in the detection of a reproduction. Authentic patina is the product of a chemical reaction that takes place over a long period of time inside the metal of the vessel when the vessel comes into contact with diverse mineral salts present in the soil in which the vessel has been buried and these chemical reactions give the surface of the bronze a certain appearance which can be granular, smooth or covered with miniscule crystals and a colour, which can be maroon (cuprite or monoxide), green (basic carbonate of copper), commonly called malachite, or blue (carbonate of copper), called azurite."

On the vessel I have green (malachite), blue (azurite)and rust-colored (cuprite) patina is present which in some places is granular, in other places smooth. Corrosion coming from inside the metal also seem to be present - I'm a little unsure of this however as my experience with archaic bronze is very limited.

Here is a case study of an archaic bronze piece that passed all the tests in Tony allen's book. It also passed an Oxford TL-test but in the end it still turned out to be a fake.

https://asianart.com/phpforum/index.php?method=detailAll&Id=61950

Thanks for sharing all that; it was very interesting. I doubt I would be able help,  but maybe if you post some close-ups of the patination on yours, someone else might.

I thought about that but it will take a while before I can make close-ups. I just got myself a new computer that I'm not familiar with so unless I can figure out how to make close-ups on this computer I will have to wait until after christmas.

@avatar This is an area that I feel needs mentorship with people who have experience handling these objects and could show us in person what to look for. Otherwise, it seems we are just feeling our way in the dark. Notice how they mentioned that sometimes it is the weight or feel of the object which is the tell. There is simply no way to have that sensitivity without handling authentic objects ourselves and being shown by someone who knows.  

Here are a couple of close-ups of the patina just to show the colors. Not the best but it's the best I could do so far.

First one is from inside the lid of the vessel:

Second is from the base of the vessel:

I might have to eat my words about azurite formation. It was those dark spots seen on the pictures I thought of as blue but now when looking again they appear more like dark gray in color. But you can see that the patina has a grainy texture.

I don’t feel corrosion tell us anything I have put bronze in the garden and in two years looks like a 1000 years old. We would need to see a the entire price. I have seen many bronzes in museums and owned a few. But yes an expert is needed for rare pieces. Bronze is being faked like everything else.

@johnshoe I know what you mean.  Such a piece would probably have to handled by a specialist and/or various scientific tests would have to be made which would by the way probably be a costly affair.

But I was asking more about the the patina that sticks well to the surface and especially if the acetone/alcohol test could be trusted.

@lotusblack/Brian Crowe I was also wondering about that but it is what Christian Deydier who is a real expert write in his article.

A short update.

I've done some more examinations of the patina and it turns out that the patina CAN be scraped off - at least in some places - using more force. I don't think that's a good sign. so I just changed my own position on this piece from being 'possibly authentic' to being 'most likely a replica'. Unfortunately.

Now I would be very pleased if some experienced person contributed to this thread and told me there are real archaic bronze where the patina can be scrabed off fairly easy but that would probably be wishfull thinking ...

Even more confusing is the fact that genuine archaic bronze piece with artificially introduced patina are also known.

A quote from the article by Deydier:

´"Fakely patinated genuine vessels

It is important to note, however, that the presence of artificial patina on a vessel does not absolutely prove that the vessel in question is an outright fake. Many authentic archaic vessels have been heavily restored and have been repatinated, which was an especially common practice at the beginning of the twentieth century."

That COULD - possibly - be the case here. But again: It is most likely wishfull thinking.

About the piece: I'd prefer not to show pictures of it so far but it's identical to a piece in a Chinese museum and searching online I found a couple of modern copies where it's fairly easy to see they are just fakes. The one I have is a much more convincingly looking replica - if it really is a replica. I could post the one in the museum and the modern copies of it - eventually with some close-ups of my own piece. I'll have to think it over.

I'm also not sure about the thing with the patina that can be scraped off easily.

I just did a search on the web to see if I could find some more information and came across this video about the conservation of an ancient bronze lamps. You can see how they use wooden sticks, brushes, cotton swaps and scalpels to remove patina that appear to come of fairly easy but it's possibly they have added a chemical first to loosen it?