F5 oddity?

[Dusty]

First time this year I ventured out into the cold for a half hour detecting on outskirts of a football pitch. Had been there once with the SE and only found a 1967 3 pence piece.

Anyhow this is not so much a problem but more a 'I don't know what's going on' type of thing. GB the machine all is good, the land showed low FE and for once I could crank up the gain to 99 without it throwing a dicky fit but settled for a modest 85 and discriminated out nothing but iron...

The first hit was a lovely flutey 75 and immediately thinking silver I dug only to un-earth some type of badly corroded metal 

The second odd thing and it has a habit of doing this on a regular is finding lots of 90+ targets albeit very quieted then loosing them, the meter will still show a variation but no sound, if I persist it will now and then spring back up with audio.. very odd 

On the plus I came away with £1.43.. not quite jackpot but a finds a find