ROMFI has the feature where owners of a particular model can post it into the main reference page. This has 2 advantages
1.) people can see all surviving models
2.) one can keep a detailed list of ones collection

As you see above, there are also fields that summarise range of known serial numbers, an average price, etc
And also when one sees an item being sold one can note the price in ROMFI and so build up an overview of prices of an item. ROMFI also solves this in an interesting manner by asking the condition of the item so as to give a differentiated overview

However it does need a certain critical mass as you see in order to be useful. One has to give in order to get!
VIEW ITEMS
Here you can see pictures with serial numbers and some details of similar models like the main reference model.

(pity about the 279825 wreck! obviously one of the the $58 bad machines)
MY COLLECTION(only you can see this as its protected behind your user ID & password)
As you add items to the "Yes I have one" section in the individual product, a summary of your own collection is also created.

One can see it in summary form

as well as in full detail

If you sell an item out of your collection you can click the "sold" feature and this goes off your collection list into your sold items list.
I hope this helps!