I'm trying to find a 1971 Killebrew Topps coin in a PSA 7 or 8 holder that actually looks like a 7 or 8, but the only ones I've seen have rim corrosion and look no better than vg-ex. Is it safe to assume that PSA (and other) slabs offer little or no protection from rust, and some of these high-grade Topps coins actually "lose grade" while holdered?

Anyone know of other items that may not retain their condition in their slab? 1956 Topps, MLBPA and miscellaneous early vintage pins? Citgo and other Topps coins?

Also, does anyone know if PSA has ever slabbed a Topps baseball plak, and if so, did it get a numerical grade?

Thanks.