I've seen more than a few Graflex cameras with lenses one size smaller than is listed in the Graflex catalogue for that model.

The same maker, i.e. B&L, just one size smaller.

Was this a common practice? Why was it done?

Could be as simple as people made their own changes over the years, and as to why Graflex would do it, who knows, they did many different things over the years.

Dave

Hmm. I'm not sure what you mean by one size smaller--and not in the Graflex catalog.
The 127mm Ektar/Optar/Raptar is offically "a one size smaller" lens because was designed to cover 3x4, but those are all over the Graflex catalog.

Now I've seen 4x5 cameras with 101mm lenses on them, but that's because the previous owner was using a roll back and wanted a normal lens for 120.

Now on the SLR side, the 'normal' lens for a 4x5 Graflex SLR (Ie series B,D, Auto) is one size larger. It's common to find a 5x7 B&L Ic Tessar on an 4x5 Auto Graflex. Or later a 190mm on a 4x5 Super D, when a 135mm is considered normal.

This is because the mirror takes up too much room, so the distance from the ground glass to the lens is longer than the normal focal length for the film format, thus Graflex SLRs have longer than normal lenses.

When Graphics were used by journalists they liked the mild wide-angle of the 127/135mm lenses so they could get close and still get everything in the frame they wanted to.
A 127mm Ektar is not a bad lens, you can still have a 8x10 enlargement that is a fair crop, and the corners of the image won't look to bad.