[Ron Ramirez]

It isn't.

There are several different versions of the 89B.

https://philcoradio.com/library/index.ph...-model-89/

The first three cathedral cabinets shown use what is commonly known as "70/90" grille cloth because it is the same pattern used in model 70 and 90 cathedrals.

Exact duplicates of this cloth are no longer available. Close substitutes:

http://www.radiodaze.com/grille-cloth-02-item-grc02/
https://www.ebay.com/itm/183963258584

The June 1934 version used a diamond pattern similar to this:

http://www.radiodaze.com/grille-cloth-05-item-grc05/

Note that the green stripes should be vertical, not horizontal.

And the final version (January 1936) used what is commonly known as "Ribbed" cloth. A close substitute:

http://www.radiodaze.com/grille-cloth-14-item-grc14/