Do not remove spacers (if equipped) on the side walls and/or on the back of the built-in
oven. These spacers center the oven in the space provided. The oven must be centered to prevent
excess heat buildup that may result in heat damage or fire
thats from your install instructions, ive seen several wall ovens trip safety therm cause the installer removed the spacers then wedge the oven into an opening that was too small
as for a model/serial tag that has been removed.... once frigidaire "writes-off" a unit for either extensive damage or repeated service while under warranty the dealer that exchanges the unit has to remove the serial tag and mail it back to frigidaire, in most cases the unit is supposed to be scrapped after that but many dealers turn around and resell them as "scratch and dent" units