There is nothing by default added to your work objects that differentiates on what was used to generate the work object related to mashup gadget, portal or other.
There is a pxRequestor.clientMode property that is set to "IAC" when using the IACAuthentication activity in step 5 (OTB). You might be using this for authentication for you Mashup. You could use the value of this property to set the value of a "createdClientMode" property on you pyWorkPage for your work object.
So, nothing by default but there are ways you can determine what you want.