I can find no reference to this Le Tigre No 3 fountain pen. A Google search found a later No 3, a post-war pen with a metal cap.
This one is a large pen:
Cap 8.3cm long, 1.6cm wide
Nib 2.7cm long from section to end of nib, 1cm wide at the widest part
Capped it is 16.2cm long (perhaps a touch over)
The closest example I found was in Jonathan Donahaye’s list. It was an earlier pen with a flange lever. For comparison, to show its size, I include it in a photo with several other Conway Stewart pens.
The very large nib with deeply incised engraving.
The tiger head clip imprint.
Thanks to Nick Lane for photographs and information.