I bought a 3.9 serp motor supposed ,( yeah ,I know

)to have been serviced by a reputable firm and only have 120,000 km. Everything was fine till I got the heads off and then I find pistons fitted backwards , some at least are
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Do these pistons get chucked in any old how or are some of these in back to front?
These two pistons are side by side ......one surely had to be arse about face ?