How can I delete catalog items of fake/fantasy banknotes (or coins)?

like this:

N#365402

You, can not. What you can do is, supported by evidence, argue your point for deletion (less likely) or moving it to another category.

This note does not exist, it is made in photoshop. Hungarian market is full of fantasy productions. 

Adding it to a numismatic catalog is a mistake. 

I am showing an another example (it is not on numista, not yet).

A note made in photoshop and printed using a color laser printer:

notafiliakp

Adding it to a numismatic catalog is a mistake. 

Hello,
Having banknote replicas and fantasy banknotes on Numista has some value, as long as they are correctly categorized.

It helps people who come across such items understand that they are not genuine banknotes and understand what they are.

Adding fantasy banknotes to numismatic catalogs is a very bad idea.

Simply, anyone can make in photoshop endless amount of variants.

…or simply generate it using AI.

They have no conections to history, arts or culture. They are just noise in the collectors world.

I have just generated a Hungarian 1000 korona fantasy note:

Hello,

Numista is a collaborative catalog, so there's a great deal of trust placed in members who add items (weight, dimensions, etc. cannot be verified). When in doubt, we ask for additional informations and references. For now, we're still able to differentiate between a digital image and a photo of a real item, for example.

Returning to N#365402 , what you can do as Idolenz said, based on evidence, is argue your point of view, the local referent will process this request.

Polette

. For now, we're still able to differentiate between a digital image and a photo of a real item, for example.

…but you cant see it is just a manipulated  photo of a 10 forint 1946. 

Texts like “TIZMILLIARD PENGO” are in modern font style.  

Stories like this are just generated by the dealers to sell their fantasy notes:
"It was printed in 1946 June 10 as a plan of the very last Pengő series which included such high denonimations such as the Ten Million Bilpengő.
This Pengő was the predecessor of the 10 Forint with different colours and a less harder colour put into it.
Although the banknote was planned to be released as the most special one that differs, due to the huge differences with the other banknotes that were already high to Bilpengő or Milpengő and due to the fact they were planning on the introduction of the Forint ,and this was the main base for the new 10 Forint, it was not issued."