(Obfuscated) Certificates as divisible arbitrary-valued currency

[barkayb]

In a previous topic of mine, I've started a discussion regarding the idea of keeping value from being slice-able by governments (or any third-party, like Mafias, I guess). The main example was pro-bono work, which is indivisible and arbitrary in value, thus making it difficult to tax or inflate.
 
An idea of mine which I'd like to discuss, but has a many-to-one relationship with the aforemened post is making pro-bono work divisible, and perhaps somewhat more secure, but still maintain value arbitrarity.
 
An "obfuscated" certificate would be a promise for work or goods, for example.
If I am a jewel-maker, then I can perhaps issue a certificate that looks as follows:

John Doe Jewels
Promise for 5 x Light jewelry work category

Authenticity details:
[Promise hash]
[QR code]

You can use the QR code to check for current ownership, and perhaps predicate change of ownership based on that another certificate is similarly predicated, or issued thus commencing safe trade.
 
These certificates are not very divisible, but they still are somewhat divisible (more so than whole products), and they still maintain arbitrariness in terms of their value. They could be inflated, of course, but that can be prevented (along with scam businesses) by having co-signers which insure or partake in the formation of the certificate:

John Doe Jewels
Promise for 5 x Light jewelry work category

OR

Mary Jane Bakery
Promise for 20 Medium Baked Goods

OR 

...

Authenticity details:
[Promise hash]
[QR code]

So in this example, Mary Jane Barkery, a business which trusts and affiliates with John Doe Jewelry is co-signing the certificate by saying "These 5 x Light jewelry... - Are worth 20 of my medium baked goods, and if John Doe won't take the cert, I will, for the specified goods.", therefore each of these businesses are insuring the customers of each-other, thus forming trust in that the promise will be followed.

 

What do you think?

 

Are there any intrinsic problems besides the value ambiguity with this sort of trade system?

What would it take to make this sort of trade system illegal? I am hoping for that expressing illegality for it would be extremely difficult without making it illegal for children to exchange candy, or making it illegal to serve dinner to family.

Do you have other better ideas? Similar historical attempts that have failed? (Or, succeeded?)