Hi Anna59,
Welcome to the Forum.
I'm not aware of any reference that particularly refers to the colonial period of Burma, hopefully someone will prove me wrong.
It would be great if you could share with us any knowledge you have on this subject.
Some details of P. Orr & Sons, Rangoon branch can be found here:
viewtopic.php?f=38&t=19329And here's an advertisement from P. Klier & Co. of Rangoon

P. Klier & Co. - Rangoon - 1903
and from F. Beato Ltd. whose head office, as can be seen, was in Mandalay.

F. Beato Ltd. - Mandalay - 1903
Trev.