Non-US Market SIL GP's are for most intents and purposes the same as the Italian GP/DL models they are related to. Things get very grey with these in the US as a lot of them are rebadged Vijai Super models that were "restored" in India to look like the original SIL non-US market export model.
If you have a square headlight SIL GP in the United States that is badged as a Lambretta, than it most likely was never originally sold in the US. The only exception to this rule is due to tastes and preferences, it is common for actual US model SIL GP's to have the SX/Serveta style headlight to be s