When the data is stored from an PB OLE Control, the application that is handling the OLE data adds an OLE wrapper around the data. It's that application that determines what that wrapper looks like, so it varies.
What you can do is store out the blob data and then use a Compound File Explorer program to examine it and see what the structure is. Then you can write code that parses out the data from the wrapper for each different application that was used.
See the following thread for a discussion of it:
translation from OLE blob to bitmap issue in powerbuilder - Stack Overflow
