CPV 51000000 is a division — the broadest level of the Common Procurement Vocabulary, identified by the first two digits of the code. Any tender whose CPV code starts 51 is classified as installation services (except software), whatever the remaining digits say.
The division splits into 4 groups at the three-digit level, covering installation services of electrical and mechanical equipment, installation services of machinery and equipment, installation services of computers and office equipment, installation services of guidance and control systems. Buyers pick the most specific code that fits, so a contract for one of those narrower categories will carry a longer code that still begins 51.
Every CPV code is eight digits followed by a check digit after a hyphen, and the digits narrow from left to right: the first two are the division, the third marks the group, the fourth the class and the fifth the category, with the remaining digits available for finer distinctions. Trailing zeros mean "no further detail", which is why the division 51 is written 51000000 rather than just 51. The check digit is a validation digit only — it carries no meaning about what is being bought, and notices sometimes omit it.
CPV codes are language-independent: the same code means the same thing in a Polish notice as in a Finnish one. That makes searching by code far more reliable than searching by keyword across markets, where the same work is described in a dozen different languages and wordings. It is also why a buyer's own description of a contract is a poor filter and the code is a good one.
A notice carries one main CPV code and may carry additional ones for the other things the contract covers, so a contract classified elsewhere can still involve installation services (except software). When you set up alerts, match on the shortest prefix that still describes your work: too specific and you miss contracts a buyer classified one level up, too broad and you read a great deal that does not apply to you. The live counts below show where contracts under this code are actually being published.
