Revision: "per node" version ID I have revisions active for a content type, called e.g. "procedures".

When a node of this type is revised, a new vid is assigned, which is a number independent of the number of revisions made on THAT node.

Given the nature of the node, I need to show/store in the node the revision number in a more meaningful way, for example version=1 for the original node, version=2 for the first revision and so on.
[edit]: I need to store this information in the database, so that it can be queried whenever it's needed. Also, it needs not to change when a old revision is deleted. 

How can obtain such result in a easy, clean way?
You can add an integer field to your node, and set the default value to 0.

Then in a small module, use hook_node_presave to increment its value every time the node is saved (or if you detect a field change). Quick, easy and efficient way.

You can do the same with a computed field, by incremeting the value of the field by 1 when you submit the form,  but storing code in the database isn't advised.