I can't say that a particular card got me into collecting, it was probably more my oldest brother who passed along his collection from the 60's to myself and my other brother that spurred me to collect the current (1970's issues, starting with 1975 Topps). And my mom helped foster this passion by always needing something from the grocery store that was 1/2 mile away, and I was given a quarter to walk there to get it. When she found out that I was spending that money on buying cards, I feel she stepped up her needs for me to make a grocery run
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There is definitely a vintage card that spurred me to immediately (actually within a year) stop collecting contemporary cards and switch to strictly prewar. It is the shown T206 of Mathewson that I picked up, along with 4 other 1910 era HOF'ers, at a card show in the early 80's. The other cards were cool too, but this Matty card in particular just caught my attention and I haven't been able to shake the hobby since.
Brian