HI Bev,
I do not know what numbers will come up on the AT Pro but because Platinum has a similar electrical conductivity to soft iron then two targets, one of iron and the other platinum of similar weights shape and size should produce similar readings and tones on the Pro. So all I can say is that platinum will show over the same range as clean non rusted iron. of cource if it is plated or alloyed with some other metal then all of this will change.
Jewelery and coin hunters rarely find platinum items because they often disc out iron.
a detector like the Explorer that reads both conductivity and ferrous content will possibly give platinum a different TID number and icon location than an iron item of similar size,shape and weight.
The number 106 in the list is actually 10 x 10 to the power minus 6 ( I couldn't figure how to print it up correctly, coz I iz not berry clebber wif key boards)