From the images on the web site linked to above, I'd say that your lens mount looks most like an Olympus OM mount.

The truth is, either of them would probably suit you equally well. The focal length difference of 15mm might make a difference and I'd probably choose that if I were faced with your dilemma.

My own preference is 180mm but If I were buying today, I'd go for the Sigma 150mm (if they still make it in Pentax fit).

The way I see it, my collection of Pentax lenses has suddenly increased in value, which is a pleasant change. I'm happy with the perceived increase in prices.

If I were to sell some of them in a month or two I might even get back what I paid for them.

Come to think of it, I could probably sell most of them, buy Sigma equivalents, and have a wedge of cash left over to buy a Canon body and a MP-E 65mm Macro lens . . . but I probably won't.

Having looked at your images of the lens mount, I don't know what mount it is, but it doesn't look like a Pentax mount.

Look at any of your other Pentax lens mounts. If you compare the three lugs that form the bayonet on the lens, on the Pentax lens you will notice that two of those bayonet legs have one rounded end and one squared end with the two squared ends facing each other.

Your Sigma lens appears not to have those squared ends to the bayonet lugs.

My terminology may not be perfect but if you look at the Pentax lens you should see what I'm referring to.

If I'm right, the lens was incorrectly described as "Pentax fit".

I didn't see that.

It's on the Japan web site here.

Can you provide some photos of the lens, in particular showing the mount and any lettering on the lens.

If it's a K mount lens, it should fit, but don't force it.

The mount mechanics, lug spacing etc. should be almost identical to your other lenses. it's only the electrical contacts and aperture mechanism that will be different.

Lens arrived in good shape. Faultless transaction. Thanks John.

Thanks.

I think that this thread would be more appropriately entitled "Pentax/Ricoh putting prices up".

Further, I think its wholly inappropriate and totally unfair to target one particular dealer when all dealers will be putting their prices up when their existing stock is exhausted and replenished with new.

If SRS are putting their prices up sooner than other dealers, it's probably for very good reasons which I think Chris has already explained adequately.

Pentax/Ricoh alone is responsible for these increases for, as yet, undisclosed reasons, not SRS Microsystems.