Bosch spark plugs 582, R3

[babyduke]

X5 3.0i 126K miles

Just replaced the spark plugs with NGK Iridium. Much easier than I thought thanks to youtube videos and feedback from many of you here. Also, picking up this magnetic was huge! Gear Wrench 5/8" x 6" Magnetic Swivel Spark Plug Socket 80546: Advance Auto Parts

Couple questions
1) Old spark plugs removed were Bosch 582 R3 and it had BMW stamped on it. Does this mean they were replaced before? I first leased for 3yrs then purchased my X5 so technically I'm the original owner. If they were replaced, I'm assuming it was done at the dealership when I ended the lease and purchased it. It had to go through a complete inspection/service before I took possession.

2) I purchased the NGK Iridium spark plugs from Amazon. Car runs fine after I replaced them but how do I know these 6 spark plugs are all good?