There is 1 John Hasler bassoon in the Hichwa-Rachor database. He flourished in London from a1830-p1844. In 1835 he was listed as a “Clarinet and Bassoon Maker”.
John Hasler Literature
Jansen, Will. The Bassoon: Its History, Construction, Makers, Players and Music. Frits Knuf, 1978 Vol. 1, p. 392.
Lasocki, David. “New Light on Eighteenth-Century English Woodwind Makers from Newspaper Advertisements”. The Galpin Society Journal, Vol. 63, May 2010, pp. 102.
Rice, Albert. Four Centuries of Musical Instruments. 2015, p. 175.
Waterhouse, William. The New Langwill Index Tony Bingham, 1993.