Magnetic shielding for Sierra-1

I am settling on some Sierra-1's and the ordering gives you the option of adding magnetic shielding for an additional $40. Although I don't have any CRT display etc, are there
any other situations where having the shielding would be needed? For example it seems
like it is worth adding this on, for any future issues (e.g., setting a wallet with
magnetic strip credit cards on top, etc). And it would be better to do it now rather
than be sorry later.

Also, I assume the shielding is a metal cover of some
sort or another than covers the (mainly) woofer magnet. Does any one know if this
affects the audio quality in any way? Thank you. Joe

It doesn't affect sound quality.

That said, I have never heard/read of anybody having any issue with non-shielded speakers and credit cards.

Thanks Curtis, I appreciate your reply. Until it showed up as an option on the
online ordering page, I hadn't given the topic too much thought, since CRT's are
rarely found in home systems anymore. --Joe

There was a discussion on this a few weeks ago but I don't recall what thread it was in.

The magnetic flux, or gauss, generated by the woofer's magnet is very minimal even right up against the cabinet. The CRT sets were extremely sensitive to any external magnetic fields and close proximity to a speaker could cause distortion on the screen and could become permanent with prolonged exposure.

I would not worry about it.