Brilhart mouthpieces. An attempt at a Time Line
Below is my best guess on the production year based on information collected for almost 5000 Brilharts with serial numbers.

I have not included Streamlines, Tonalites and Level-Air. Nor the pieces Made in England. 
NB! Streamlines and clarinet pieces did NOT have Great Neck printed on them

Start- and end-serials for each period are those I have in my files, not necessarily the exact numbers where the period changed.

In February 1951, Personalines were introduced, and at the same time they started all over with the serial numbers, the so-called small font.
While they had used parallel serial number lines for each type of mouthpiece since Great Neck, they now switched to only one line of serials.

NB!  The Level-Air metal mouthpieces changed to date-based serials after the Selmer take-over and Selmer continued with this kind of serial numbers for the Level-Air only until they stopped production, probably in the 1980's.

For questions or comments, send an email to:    donottoand AT gmail (dot) com (Substitute @ for AT)

Simple, arial-like font
Large, old-fashioned font
Small font
Selmer serial (Date of manufacture. MMDDYY)

The mystery about the missing Hard Rubber mouthpieces.

My lists have almost continuous serial numbers between the end of Great Neck period and beginning of Mineola.
For Ebolin: Alto: 108xxx - 111748, (3000 missing), Tenor: 78958 - 79806 (848 missing),
and for Tonalin: Alto: 96427 - 98394 (appr. 2000 missing), Tenor: 76806 - 76836 (30 missing).

But when it comes to hard rubber, the gap is much bigger.
Alto 8362 - 31715 (more than 23000 missing) and Tenor: 7900 - 37097 (appr. 29.000 missing).
Is the explanation that Brilhart had problems getting hard rubber blanks during WW II. ??

Overall time line