Yanni Giftakis recommends melting crayons into the letter groves of typewriter keytops to replace their missing paint with a heat gun, much the same way D&D players will fill in the groves on their dice.

This is similar to Richard Polt's recommendation "To restore faded paint on keys and scales, try Lacquer-Stik Fill-In Paint."

via https://www.facebook.com/groups/typewritermaintenance/posts/3831371387100282/

On many of the older 40s/50s typewriters, the same key will work on almost everything. If you search online there are a few people who have posted a 3D printable key that you can download and may be able to print at your local library. I'm guessing based on the limited photo, yours is an early 40s Smith-Corona.

I've tried a few local locksmiths who don't seem to carry these keys anymore.

I've got a late 40s Smith-Corona latch that occasionally self-locks and for ages I used a bent paperclip in the rough shape of the old keys to easily pick the lock with just 10 seconds of jiggling around inside. Roughly a 2 mm straight section of paperclip with a 1mm "T" section that sticks out (even just on one side) about 4-5mm and then continues straight ought to work if you're in a jam.

The level of security these keys/locks provide is minimal at best.

If you go the online route to buy a key, they can be quite expensive, so if you're a collector, just wait for a machine that comes with one and you'll have another typewriter for "free" in the deal.

reply to u/Succu6us66 at https://old.reddit.com/r/typewriters/comments/1eqk6rd/typewriter_lock/

Distinguishing Ukranian vs. Russian typewriter keyboards

via u/lexkiri at https://new.reddit.com/r/typewriters/comments/1eloo76/russian_american/

reply to u/Deep-Seaworthiness48 at https://www.reddit.com/r/typewriters/comments/1e5gh4p/two_5_keys_sc_poweriter/

Things like that happened on alternate language/region typewriters. I've got a Dutch keyboard layout that repeats a % symbol twice.

It's likely that the pound symbol was needed/required so they pulled one from a pre-existing typeslug and key cap on a keyboard where the £/5 key was common and replaced the 1/! which in the era was widely known could be done by alternate means (aka lower case 'l' and '.' backspace '''.

The value of the £ was more important to the typist and because of typeface manufacture was probably easier to do in the £/5 existing combination from something like the English No. 1028, International No. 1060 keyboard, the Brazilian No. 1065, or the Danish No. 1047 all of which paired the £/5. See also: https://munk.org/typecast/2023/02/03/1954-smith-corona-scm-typewriter-type-styles-and-keyboards-catalog/

Off hand, I don't see another S-C keyboard combination from that time period that had a £ paired with any other glyph/character. In the "change-a-type" time period they likely wouldn't have done a custom black key for the £/5 when they were already manufacturing one in a matching white. If they didn't also swap out the key at the far right end of that bank, I would expect it to be a standard black '+/=' key cap and slug.

1960 Union Foundry Typewriter Type Slug Specifications – To Type, Shoot Straight, and Speak the Truth… by [[Theodore Munk]]

Type Shop, Ep. 15: The Ultimate Keyring Toolset Guide by [[Typewriter Chicago]]

Charles Gu's new keyring pliers for about $500 for a set are as good as if not better than vintage tools. In particular the new rubber pieces seem to help protect from breaking the original glass key tops which will then require replacement.

Tips for Removing and Installing Olympia SM3/SM4 spring loaded typewriter keys by [[The HotRod Typewriter Co.]]

For yellowed glass keys on typewriters, there's usually a key top covered by a piece of paper with the key glyph on it which is sandwiched in with a small piece of glass and a metal ring that holds it down with several metal tabs underneath the key to hold it all in place. There are custom keyring pliers for quickly removing and replacing the papers which needs care not to crack the glass. Otherwise you can manually bend the metal tabs on all your key rings to remove them and replace the papers. (This is generally a LOT of work either way.) See: https://www.reddit.com/r/typewriters/comments/1csni4d/neat_find_on_clients_kmg/

I prefer the yellowed patina of the older key papers, so I tend to leave them versus spending the time and effort to replace them.

Keyring pliers are used to remove the metal rings off of both circular and tombstone glass typewriter keys so that the legends can be replaced or even covered over with black paper circles for teaching or learning typing. They take some practice and skill to use, but speed up the replacement of legends significantly.

Wiping dirty plastic typewriter keys with a soft cloth and then waxing/buffing them can bring them back to life.

Smith Corona Vintage Typewriter Straighten Chrome Ring Keytops Twisted Crooked Letters Repair by [[Phoenix Typewriter]]

Royal Quiet De Luxe Typewriter Sticky Keys Segment Flush Clean by [[Phoenix Typewriter]]

https://www.reddit.com/r/typewriters/comments/2rru4x/where_can_i_buy_the_key_to_the_case_of_a_smith/