Following a recent prop overhaul, mt put this ugly sticker on my prop, despite me asking them to NOT put any such stuff on the prop. Question: is this a legally required placard by FAA rules following an overhaul? I wouldn‘t think so…
It appears to be a Hartzell prop, and if so no such placard will be listed in the TCDS. Overhaul records are kept in the propeller logbook.
To sort of answer my own question, I guess that while of course one does have to have a placard on the prop which shows the prop model designation and the S/N, but I guess it does not have to „branded“ by an overhaul shop. I checked older pics of the (factory new) prop, and while there was some similar thing on it, it was less colourful and therefore less conspicious.
I didn’t have such placard on TB20 prop and had heavy fight with CAA (EASA-reg) when extending airworthiness. In the end I was right, it was metal propeller with engraved serial number and proper paperwork in aircraft service logs. However, I lost few days in proving my case.
I am not sure about legality of sticking an overhaul placard? but isn’t that moot if your propeller overhaul is not mandatory in the first place?
I am assuming it’s for Part-91 with no AD
I guess that while of course one does have to have a placard on the prop which shows the prop model designation and the S/N
Only if the MM states that. However, that data can be attached to the hub, not the blades.
If there is no S/N placard, then there is no tie-in with maintenance documentation, and you could end up having to scrap it. I heard somebody did that with some airliner landing gear…
but I guess it does not have to „branded“ by an overhaul shop
Totally correct – advertising is not required 
But most/all prop shops do this.
If you do not like the look at all how about putting some plain white sticker over it? So you do not see it but if there is ever any discussion you can undo it. It saw this sticker any many props done by MT and I assume putting it is in their quality manual etc. so not doing so is not so easy for them.
Perhaps it can be put on the rear of the blade near the root where it is largely hidden by the cowling?
To sort of answer my own question, I guess that while of course one does have to have a placard on the prop which shows the prop model designation and the S/N, but I guess it does not have to „branded“ by an overhaul shop.
All the parts were impression stamped at manufacture by Hartzell, there is no need for a sticker from the overhaul shop (or anybody else) to reference the assembly or component serial numbers to the overhaul records in the propeller logbook. Maintenance logbook records are what is relevant for US registered aircraft if (hypothetically) operation outside of Part 91 requires something other than propeller maintenance on condition.
If the aircraft were Canadian, the following excerpt from the regulations would apply:
Information Relating to Aircraft Engines and Propellers
201.08 The identification information that shall be placed on an aircraft engine, aircraft engine module, fixed pitch propeller, propeller blade and propeller hub is
(a) the name of the manufacturer and, if the manufacturer is an entity, its legal name; (b) the manufacturer’s model designation as described in the type certificate or equivalent document; (c) the type certificate number or equivalent designation; (d) the aeronautical product serial number; and (e) in the case of an aircraft engine, the power rating established for the engine by the manufacturer.QuoteAnd,
201.12 (1) No person shall remove or replace an identification plate attached to an aeronautical product that is not an aircraft or alter the identification information that is required by section 201.06, 201.07, 201.09, 201.10 or 201.11 to be on an aeronautical product that is not an aircraft unless a written application is submitted to the Minister, including evidence that establishes the identity of the aeronautical product, and a written authorization is issued by the Minister pursuant to subsection (4). QuoteRemoval and Replacement of Identification Plates and Alteration of Identification Information on Aeronautical Products Other Than Aircraft
I don’t know the FAA regulations well, but they’re usually really similar to Transport Canada regulations.
When I changed the flight authority basis for my airplane, which requires a change to the data plates for the airplane, engine, and propeller, I sought, and received authorization from Transport Canada to make the change. Removing the data plate was not an option.
