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Nice photo.
Indeed, this is an
outstanding "looking" lens. The blueing on it is among the best I've seen (deep/dark/rich). Be sure to bring along a clean cloth to regularly wipe the fingerprints off of this "looker".
If you can find a minty copy and take it out to a site where the BIF photographers hang out, I guarantee that it will get some unsolicited comments on how nice it looks (although the folks shooting fast/expensive/auto-focus Nikkors and Canons will get many more keepers than you will



).
P.S. I thought that I'd mention that the balance of this lens with a Pentax K-1 (without a grip on it) is almost perfect. Because of that, it's not at all awkward to handle on a good tripod/head.
P.S.S. Put one of the longer extension tubes on it and it's closest focus point goes from 30 feet to about 10 -12 feet - plenty close for some
serious butterfly photography.