To be honest Neil, I'm surprised you've posed this question ... are you winding us up?
The Property (Asset Number) and "BME" (Equipment Control) Number can - should - have different purposes; and - probably more importantly - they are managed by two different departments. In short, one is for keeping track of physical assets above a certain value ("bean counting") whilst the other is for identifying equipment for tech support purposes.
In every place I have had a say in managing biomed kit, I have found a need to have some sort of "cross-reference" number to pin down equipment at least by manufacturer and model (ie,
"type") when trying to organise (make sense) of equipment management. On a number of occasions I had tried using the existing "equipment tags" that were imposed upon me for various (usually contractual) reasons, but they always fell short. As you know Neil, I have many stories to tell, but suffice to say that having an Equipment Control Numbering system - based on a semi-meaningful code structure - has always "won through".
I have also seen many types of Property Tag (Asset Number) schemes, as well as "numbers" stemming back from the construction contractor in "turn-key" hospital projects. None of them have been especially useful for the biomeds. As we all must have seen, some kit (x-ray systems, ultrasound units) may have any number of "Asset Stickers" plastered all over them.
On the other hand, even chairs (for example) have Asset Numbers. These are usually serial numbers (often long), although they can also be based upon a semi-meaningful structure (but never with "biomed" in mind, as far as I have seen). Although it may not matter to some (non-OCD?) observers, I have found that lists of assets almost always contain mysterious (but inelegant) gaps in the numbering series - as well as duplicate numbers!
But in any case, if both numbers (or codes) are recorded, they only take up two fields in a database.
If you were looking at this stuff from the point of view of the user - and why not - as in "which number do they call through" (when reporting faults or seeking assistance) ... I would say "use the Property (Asset) No." - on the grounds that this would be the one they are most familiar with. The "BME" number, fixed on the back of the equipment next to the manufacturer's plate, would be (is) for "our" - the biomeds' - use only.
As you have suggested on many occasions Neil - and I agree with you - the biomed department needs to be independent (free) of the whims of other "fly-by-nights" who like to impose their brilliant ideas on those doing the real work ... I'm thinking here of "IT", the "bean counters" and the property management team.
One last thing - don't forget RFID (hint:- another field or two in the database).