Converter MUST have stamp, Headers must have stamp, everything else has stickers; if the sticker is missing on such things you can do part number to EO# with a little investigation. If you can't see the part number then a internet visual match to EO is ok, but it's your call. The problem with failing for missing sticker is that a ref or other shop might pass it and then the customer can complain to BAR, and if they agree part is legal they will ask you to refund the money to the customer.
NO, the proof is on the customer to prove it is legal not us, so if there is no EO# its a fail and the BAR is in agreement with that, in fact, no sticker or stamped part then it is a guess. If you have a problem with passing it or failing it send it down the road.
The requirements for making the converters specify that it must be stamped, other things get stickers, missing sticker not grounds for failure, missing stamp is. No contradiction, just poorly stated and not geared to EO techs reading levels.
New Label Requirements
The label on the catalytic converter shell must be 1⁄2 inch high and large enough to be read from a distance of 5 feet from either side of the vehicle. The label must show the EO, specific part number (universal or direct-fit) for the vehicle, and date of production (month and year). In assigning specific part numbers, manufacturers have taken into consideration each vehicles exhaust configuration, including the location of the oxygen sensors, pipe size, etc. Therefore, no modifications should be required to fit a catalytic converter on a vehicle other than weld it in, where necessary.
To me, a key part of the argument would be the install date. In the "4-hour" online course, there was mention of a customer that had a receipt proving the installation date, but it was not explicitly stated that it was required. I see a lot of aftermarket cats in my neighborhood, and I've been forced to follow my instincts with regard to apparent date of install, since legible receipts are practically non-existent. If I didn't, I would be blowing up my SVFR, blowing up my Abort %, and/or blowing up the Referee appointment hotline.