Hello Ivo.... regret I don't understand the comment that......."The colour is slightly yellow tinged, so in any case it is pre-1920s"
I'd have thought that your comment about weight coupled with this colour was suggesting only that your funnel lacked any lead content - could be wrong, but I've always understood that a 'yellowish tinge' to mean less or no lead, and a darker or blueish colour to mean some or more lead. Date wise it could be anywhere from the C19/early C20.
I get the impression that silver examples seem frequently to include a strainer (like an old fashioned tea strainer which caught the grouts) - although obviously not really possibly with glass ones. Potential for a lot of 'lees' (sediment) to come out of C18 wine if you accidentally shook the bottle up, and it was common for the butler to line the funnels (assuming no inbuilt strainer) with linen or fabric of some kind.
It's also possible (but I've no evidence) that the 'squinted' funnel was a natural progression from the straight sort - perhaps after they'd all got fed up with a mouth full of sediment.
The distal end is often finished obliquely, as opposed to what appears on yours to be cut off at 90 degrees.
Peter may well be correct with his suggestion of late C17 - although most seem to have been in use in the C18/C19, and as Peter implies, not easy to date.
As a generalization...........dip moulded examples might be earlier than cut pieces i.e. first half C18, and thicker cut ones are probably post late C18.
The suggestion that yours is C19 is probably a safe bet, and without any specific data like cutting or design you may never know its origin or date.
Apparently, in 1795 the Earl of Breadalbane bought a glass funnel for Sterling 12 shillings and six pence (£0.62.5p), so hope you weren't robbed when buying yours
Sorry that, as usual, this is rambling and includes nothing really new, but I just love history.

Ref. 'The Decanter - An Illustrated History of Glass from 1650'. - Andy McConnell - 2004.