Help the Ageing

ahoy there all amateur underwater archaeologists.

i am trying to date this piece of water junk found in Malta near the wreck of the Maori. from the corrosion and growth, I reckon it's been there 5-10 years. yay? nay?

so, how long has it been in the water? how much of its wear was suffered at the surface?

the ultimate aim is to identify the make and model (and preferably before all my biker friends find the answer).

Thanks in advance.

PS no reward is offered, but you're free to claim the bike if you're willing to collect it.