Brilhart mouthpieces. An attempt at a Time Line
Below is my best guess on the production year based on information collected for over 3100 Brilharts with serial numbers.
Updated 16. July 2018
I have not included clarinet or baritone pieces, Streamlines and Tonalites. 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.

Before 1951, there were separate and parallel serial numbers for alto and tenor and for HR, Ebolin and Tonalin (and Tonalite).
In February 1951, Personalines were introduced, and at the same time they started all over with the serial numbers, the so-called small font.

All the mouthpiece types were now numbered within the same line. The first 2800 numbers were allocated to the Brilhart mouthpieces Made in England.

For questions or comments, send an email to:    donottoAToncable.dk (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 - 113xxx, (5000 missing), Tenor: 78958 - 79806 (848 missing),
and for Tonalin: Alto: 95495 - 98394 (appr. 2900 missing), Tenor: 76806 - 76836 (30 missing).

But when it comes to hard rubber, the gap is much bigger.
Alto 8362 - 43899 (more than 35.000 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