BidDescriptor

FIX Field 400

Tag	Name	Type	Enumerated	First introduced
400	BidDescriptor	String		FIX.4.2

BidDescriptor value. Usage depends upon BidDescriptorTyp (399).

If BidDescriptorType = 1

Industrials etc - Free text

If BidDescriptorType = 2

"FR" etc - ISO Country Codes

If BidDescriptorType = 3

FT00, FT250, STOX - Free text

Notes

Please post comments, clarifications, examples here. Click on the edit button on the right and away you go! 

Don't forget to refer to the FPL Discussion Groups to back up anything you write.
You will often find the authoritative statements on matters of FIX specification interpretation there.
Links from FIXwiki pages to relevant discussions on the FPL site are very valuable.

For example if you were writing a clarification on how to specify the "quantity" of an order in FIX, you might add the
following relevant link, http://www.fixprotocol.org/discuss/read/f5014573, to back up your points.