This plant is the Alocasia watsoniana that has been known by that name for many years; it is the very large type such as is pictured in "The Cultivated Alocasia", which is Aroideana, Vol. 7, No. 3 and 4. The much smaller Alocasia being sold as watsoniana or 'Tiffany' is not like this one at all. Taxonomists have lumped this plant in with the A. longiloba/lowii group, to which it is most certainly related.
We were able to borrow this fine specimen for use in our hybridization programs and it cooperated with two inflorescences and plenty of pollen. A. watsoniana has cultural needs similar to those of the A. sanderiana 'Nobilis' and other jewel types.
The picture above shows the A. watsoniana inflorescence at male anthesis. This pollen was used in a successful cross with Alocasia 'Borneo Giant' and the seedlings are now growing on. The hybridization success is verified as some seedlings show purplish leaf undersides, which has to have come from the A. watsoniana. Sadly, the seedlings all succumbed to some kind of infernal rot (probably damping off). Since I know the cross can take, I will attempt a repeat of the cross. Meanwhile, I have crossed A. watsoniana successfully with A. odora and obtained a wide variety of leaf types and plant sizes. Some can be seen at my hybrid page Alocasia x 'Watson's Giant'