which amp alternator

Also does anyone know which alternator i need for my P reg 1997 4.6 HSE LPG rangey? i have been told a 100amp one based on my vehicle but on the island-4x4.co.uk they say advertise that i should have a 120 amp one as i have a heated front screen. i had a look at the label but not clear but think says 100A. cheers

any other numbers on the alternator? pics wud be useful.

sorry where the sticker is positioned it is difficult to see. but i have a theory about the one installed. i was told by Universal Rotating Electrics Ltd that using my reg number their system says a 100amp alternator but on island 4x4 it says a 120 amp will be right for a 4.6 with heated screen which i have. so is it possible that the wrong unit was installed and that a bigger one is needed and therefore not as much strain on the alternator?

where could i find the actual part ref? the island 4x4 has part ref numbers in the description