I recently bought a 2020 from the original owners, and though when I got it it had no work done to it (I had to replace the headlight wire after it broke as I removed the smokebox face to replace the bulb), it has no decal. It's obviously the original face, and there is no major wear on it. Possibly left unstamped at the factory?
The 6200 Keystone was only a decal, and never stamped. Considering the age of 70 years old, the decal could easily have disintegrated over time leaving a blank Boiler front. Not uncommon at all.
Check this out, it'll tell you quite a bit about your 2020...
www.tandem-associates.com/lionel/lionel_trains_2020_loco.htm
This is the link to the whole site, very handy to have!
www.tandem-associates.com/lionel/lionelident.htm
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