Old lens with no name

[Wade D]

I recently got a lens/shutter from a friend. I appears to be quite old but works. The shutter is a Kodak Ball Bearing with 3 speeds. The lens has no writing around the front element. The rear element has "5x7 Rapid Rectilinear" on the side of the barrel. Any idea what the age and focal length are? It covers 4x5 with movements and appears to be very sharp.
Thanks,
Wade

[eddie]

photos would help.

measure from the iris to the ground glass to get a very close approximation of the FL. probably a 7 inch lens. it may convert as well. try it.

[Glenn Thoreson]

It's a Bausch & Lomb Rapid Rectilinear. The aperture scale will show it as an f/4 lens, but that is the old US system. It's actually an f/8. To get modern f/ stop settings, just remember f/16 is f/16 and count up or down in modern progression. Extremely sharp lens in the center, with rapid fall off in the corners and edges. 5X7 means it came off an old self casing plate camera from the late 19th or early 20th century, ala Premo, Seneca, et al.
Fun to use but those shutters are rarely even close. Pretty crappy actually. I've had good luck getting 1/25 out of at least one speed.
I should mention that using this lens on 4X5 will keep the image more within the range of shapness. That, to me, is the secret to using these things.

[Wade D]

It does have US stops and I have a conversion table. You're right about the shutter. It seems to be the same speed no matter what is selected. I did a little searching last night and it looks like it might be from a Seneca from around 1915. I'm going to set it up on my Crown View today and get an approximate FL.
Thanks for the replies so far.