There is insufficient information to identify this bullet. The overall length to diameter ratio looks, by eye, to be more akin to the 9 x 18m/m Police, but the ogive of the bullet would only really match a relatively scarce ogive for Geco-manufactured rounds. Most of the 9 x 18 Police/Ultra series have either bullet with ogives more like a .380, in some of the early trials rounds, or are truncated flat-point.
The scale in the picture looks to be in inches. It seems to be a pretty standard scale separated into 16ths of an inch. However, the joker there is that if it is, and the bullet and the scale are on the same level, the bullet would be approximately 7/16" of an inch in diameter, or as some one said,
somewhere around .45. Of course I agree with Lew - no ciminalist would mistake a .45 bullet for a 9mm, and this bullet is not of any normal .45 ogive. I think we can throw out the rule shown as any reliable guide to dimensions, lacking knowledge of what the graduations actually represent. It is dividided like an inch ruler, not like a metric rule, but there is something wrong somewhere in that picture! It may by the perspective of the bullet.
Needed information is the recovered weight of the bullet, the bullet jacket material (am not sure even from the picture if it is gilding metal, or was plated or tinned over gilding metal), the actual diameter of the bullet measured as best as one can (yes, the bullet is slightly deformed and that makes it hard, but even over a slightly deformed bullet, it is helpful beyond just saying it is "9mm). and if any fired cases were found at the scene. I know that latter one sounds stupid on my part, since it is so basic, but I handled the identification of a bullet where I was given “all of the information available” only to be told after pulling apart twenty or so rounds and identifying the maker that my identification was undoutedly correct, because they had found at the crime scene fired cases from that maker. Yes, I wanted to reach through the phone lines and stangle the investigator I was speaking to.
The cannelure appears to be very shallow in the picture - too shallow to be a proper crimping groove. Again, it may be just how the picture makes it look, but if it is as it looks, it could be nothing more than a ring left by crimping the case mouth into the soft copper jacket; that is, before being loaded, the bullet may not have had such a “cannelure.”
I know from other correspondence that Lew has given all the information he has. Based on just that information, it is all a guess and a gosh, not up to standards of criminal identification of evidence. More information is needed from the crime lab. They should, from the very strong rifling striations on the bullet, be able to narrow down what makes, models and calibers of gun fired it. That would be helpful to, as it could end or narrow down any argument as to the case type the cartridge came from - probably not, though, in the instance of 9mm Para and 9 x 21 Italian (IMI).