unidentified cash coin

[Afrasi]

This cash coin looks as if it was made of tin. My guess is Indonesian provenance ...

Can anybody help, please?

[bgriff99]

I suggest an edge scratch to get a better idea of the metal, and just for the process of elimination, a magnet test.   It looks to me like the low grade copper typically seen on Indonesian shima-sen.   The mineral crust looks like a tin compound.   It is compatible with being a recast from an original coin.   

Catalogs for shima-sen do not show very much in the way of direct recasts, but rather those which are original creations.    For bita-sen virtually any and every kind of N. Sung cash was directly copied.   That is, using an original coin for a mother cash directly.   But those are of copper, which tends to rust.

There are some series of tin, lead, or pewter recasts of originals, or of copper private trade cash.   I don't recognize this as one of them.

[Afrasi]

The coin is non-magnetic.
The coin (or the mother coin) is a Chêng-Ho Tung-Pao / Zheng-He Tong-Bao (Schjöth #633 / Hartill #16.428), but the top charakter matches not exactly.
I have one coin of Chêng-Ho made of brass and some others with a similar toning like this one.
The coin has a hard patina. Until now I could not scratch it with success.
Another thought is: Could it be a Japanese Kato-Sen?

[bgriff99]

At first look, 'cheng' appeared to have been recut.   But on comparison to the complete list of varieties in Kosen Daizen and scrutinizing through the surface crust, the characters are as an original piece.   The garbling in 'pao' makes it look like a recast.   The metal is not compatible with a bita-sen in any case.   

I'm guessing at the metal, but it looks like extra tin is added, which would not be done in a domestic Chinese forgery.  For each measure of tin, two of lead would be added in most places.   Only around the tin-producing areas of Sumatra, or those in commercial contact with them would tin alone, or with a smaller amount of lead be used.   It may also be an original which has simply developed an odd blackish patina.   I have a few like that.   

Coins with a high proportion of tin, say 40%, should exhibit a very hard metal.   If it was only adulterated with lead it would have a blistered look, unless it was sea salvage.    That however could also cause the blackish patina.    This is all guessing which can not be backed up without an XRF check, or archaeological connection.    If the metal is not visibly yellow, you could probably identify it as Indonesian.

Original Cheng Ho coins are made of leaded bronze.   Typically 10% tin, 18% lead, the balance copper of good quality.

[Afrasi]

Thanks for your answer! I learned something new again. Comparing it to most of my Chêng-Ho-coins I now think the material of my piece is the common one.

I found only one single Chêng-Ho-piece looking like brass. But this should be the result of an "inadequate cleaning" ...

[bgriff99]

Depending on its composition, leaded bronze can look like copper, or a lighter pink, or pale brass, or cupro-nickel.   They had nickel and sometimes used it.   Most of the "white copper" Sung cash are from using more tin and lead.    The mixtures which come closest to brass in color have less of its golden tone, and can not take or hold the high luster of brass.    This piece has the cupro-nickel look, which buffs up to be white copper, and is the normal metal for these.

Your first piece is probably beach-washed with a copper sulfide patina.

[Afrasi]

Oops! Very late ... 

... but many thanks for helping me!