#define A 65
#define Z 90

var/last_tag = "AAAAAAAAAA"

datum
    proc
        GetTag()

            // We need to make them a tag
            if(tag == null)
                tag = CreateTag()
                last_tag = tag

            // If they have one already, just return it.
            return tag

    proc
        CreateTag()

            var/current_char
            var/new_tag = ""
            
            for(var/i = 10; i >= 1; i--)

                current_char = text2ascii(last_tag, i)
                
                // A - X
                if(current_char < Z)
                    
                    // Increment and we're done
                    current_char++
                    new_tag = "[ascii2text(current_char)][new_tag]"
                    return copytext(last_tag, 1, i) + new_tag
                    
                        
                // Z
                else
                    // Turn over and keep going until we hit A - X
                    new_tag = "A[new_tag]"
                    
            
            // So you actually ran out of IDs. There was 141,167,100,000,000 possible combinations.
            // Even I'm impressed. At this point it will roll back to the start.
            return new_tag