Here's my trinity- the First Three.
1970 Original Cast Album- I've been blessed to have it autographed by Loretta Long, Bob, and Caroll Spinney. Only took twelve years to get all three autographs, but well worth the wait.
1970 The Year of Roosevelt Franklin (original pressing of 'My Name Is...') with Matt Robinson on the cover, and a neat picture inside of Joe Raposo with his headset.
1971 Sesame Street 2- worth the price of admission for "Someday Little Children". Would be great if this ever got released on CD. Until that day, I still have a working turntable.
I had the first two cast albums when I was little, and they were brand-spankin' new.
Then when I was about six, I made the huge blunder of GIVING THEM AWAY, BECAUSE I THOUGHT I OUTGREW THEM!!! Luckily, back in the 90's, I found all three of these again at garage sales, couldn't have paid more than two bucks for all of them together, and NEVER letting them out of my sight again.