I have not seen any of these relics but my understanding is that these are true:
Carisbrooke Castle on the Isle of Wight has things of King Charles I:
– A lock of King Charles I Hair
– King Charles bed when he was a prisoner
– They have other relics of King Charles I as well.
– Here is a website showing some artifacts:
The gloves which were given to Bishop Luxon on the scaffold is supposed to be located at Lambeth Palace, London.
The Museum of London is said to have some artifacts:
– A blue knitted silk shirt worn at execution
– A fragment of cloak said to be worn by Charles at his execution
– A cap of Charles I
An outer shirt worn at execution is at Windsor Castle. This may not be the original. There is speculation that it may be a female night gown. Here is a site about it:
Doublet which may have been worn at execution – Marquis of Bath, Longleat House, Warminster, Wiltshire.
The chair and footstool used at the trial is said to be at the Victoria and Albert museum. I think most people agree that these are not original but were actually made for his son, King Charles II. Here is the website:
SKCM (the Society of King Charles the Martyr) is supposed to have relics of King Charles I but I don’t know where they are located. Here is their website:
Some other items of interest:
– An interesting site about relics from King Charles I:
– Bradshaw’s hat that he wore at the trial is at Ashmolean museum, Oxford.