Ihaga may have been based in Liége. As far as I know they only produced one basic design, as used by the S.A.G. in this collection - although it may have come in two variants - one which attached to the axle and one which attached to the chainstay.
Their, very modest, claim to fame was a Quixotic, but highly rational, commitment to the idea that derailleurs should be ‘top normal’ (in an era dominated by ‘low normal’ Simplex designs). Ihaga considered that it was better to get the rider to do the ‘hard work’ of shifting the chain ‘up the hill’ onto larger cogs, allowing the spring mechanism to perform the ‘easier’ task of shifting the chain ‘down the hill’ onto smaller cogs.
I would, personally, still choose a top normal design in preference to a low normal mechanism. And it is notable that, although Shimano claim to love their low normal ‘rapid rise’ designs, every Dura-Ace derailleur ever made has been top normal.