For anyone still looking to purchase T1N door key blanks.
Amazon offers an inexpensive plated brass chip holder key, with NO CHIP.
I went down to hand cut one of the spare keys I had on hand. I bought 2 ea. thinking that they would be steel. I marked the key to begin the hand cutting process. As soon as I touched the file to it I realized that it wasn't steel. Holding it to a magnet verified that as fact.
I went out and tried the plated brass keys in all of the locks on the 2004 and the 2006. Each key inserted into all of door locks and ignition without a problem. The keys
appear to be similar in material grade to my MB17 blanks (MB17 blanks do not have the plastic handle chip holder).
I can say this.
Back in June when I purchased the keys, AT THAT TIME, the vendor was supplying plated brass keys. The price is below 3 bucks each. Any locksmith should cut these keys without any problem. They will work fine as door keys. Swap over the OEM chip from a broken key, or do the Goop glue chip trick, and it will work as an ignition key.
TOOGOO(R) New Replacement Uncut Blade Transmitters Key Shell Case for Mercedes Benz Vito Actros Sprinter V Class
https://smile.amazon.com/gp/product/B01A5732DO
Truth be told, the first 2004 rear door cylinder I tried only allowed partial insertion. That made me think the key had a problem. After the 2 ea. keys worked perfectly in all of the other 2004/2006 locks I went back to the 2004 rear door and pushed a bit harder. The key inserted, but there was a bit of shmutz on the tip of the key when I removed it. After a couple in and outs it too was fine as frog's hair.
I apply WD40 to all of my locks each Fall, AND all of my many other keys work fine in the 2004 back door. I was surprised there was any problem.
Anyway, don't hesitate to add the above Amazon keys to your list. Shipping was 3 to 6 weeks, but arrived slightly sooner than promised. Faster shipping isn't offered.
vic