I am confused about which model halolight tv I have. The label on the back cover reads model 21T103B. However when I looked up the model at the radio museum website it showed this model number as the "Balmoral". The description says that it is a table model and the picture shows the word sylvania in a different position on the front trim piece and the small knob on the left corner doesn't exist in the picture. Also it does not mention anything about a base for the tv. Any help would be appreciated.

Maybe made the same model a couple of years and changed the trim on it one year. I'd go by what's on the back.

The base is probably an option, the one on your set is likely removable since it also has a place for a speaker in the top part.
The other differences might be as Gregg suggested, a model year variation, or the B suffix might denote some minor variation, or the museum could just be wrong.

Is the small knob in the lower left corner for the brightness of the halolight?

I am confused about which model halolight tv I have. The label on the back cover reads model 21T103B. However when I looked up the model at the radio museum website it showed this model number as the "Balmoral". The description says that it is a table model and the picture shows the word sylvania in a different position on the front trim piece and the small knob on the left corner doesn't exist in the picture. Also it does not mention anything about a base for the tv. Any help would be appreciated.

Not all the Sylvanias had Halolight.
I never saw one with the small knob. The last one I worked on didn't have Halolight. As someone else stated, the small knob is probably for the Halolight brightness.

the B probably is the later version with alterations like the little knob and maybe the cabinet too , i have an emerson i think 644B , the difference is two knobs were removed from the front ( like the 10" version has ) and located in the back and they actualy have knobs on them in the back , other emersons from that point on also have just the two knobs in the front , so i'd say the sylvania is a later production with alterations

mike