illegal numbers
 

During warmups, it's noticed that 3 players (for the visitors) have illegal numbers on their jerseys.
What are the coach's options?

Either tell him they are illegal and they can not participate due to having illegal numbers per rule 3-3-d or be nice, see if it's okay with the other coach and tell him they are illegal and that they can play tonight but get them taken care of, then report them to your assignor.

If you have not reached the 10 minute mark, and the team has enough legal jerseys, have the players change and fix the lineup with no penalty.

If the 10 minute mark has been reached, they could still change jerseys and change the lineup at the cost of a team technical foul.

If the kids with the illegal jerseys aren't going to play anyway, then you don't have a problem. Of course, you won't know whether they're going to play until you talk to the coach.

If any of the three participate while wearing an illegal number, it is a direct technical foul to the head coach. Only one T is assessed no matter the number of illegal jersey infractions that occur. So, in effect, the coach can buy these kids into the game at the cost of a T.

Note that unlike 3-5, which specifically prohibits a player from participating while wearing illegal equipment and/or apparel, 3-4 does not prohibit a player from participating while wearing an illegal uniform. Assess the penalty when it is discovered that the player is participating, and move on.

(See NFHS 3-4, 3-5, 10-1-2, 10-5-4)

Illegal Uniforms (Illegal Numbers) ...
 

Technical fouls for illegal uniforms (including illegal numbers) are not charged to the team, but are charged directly to the head coach. If a team member participates as a player while wearing an illegal uniform, then a direct technical foul is charged to the head coach, who will lose the coaching box privilege for the remainder of the game. This infraction is penalized when discovered, and the team member with the illegal uniform may participate without further penalty and is not required to change the number. A maximum of one technical foul shall be charged directly to the head coach regardless of the number of offenders.

As BITS said they can participate at the cost of a direct T to the coach. If it's a Varsity game, I think your advice of "seeing if it's ok" with the other coach is misguided.

acceptable at sub-varsity levels only (and ever there, it might vary by area)

For clarity, is it also a maximum of one technical foul if a team has #0 and #00, and also has #6, or are these considered two different types of infractions?

As far as #0 and #00 go, is this penalized when the second of the these two enters the game?

Honestly, at the sub-varsity level, I wouldn't even notice this. I wouldn't even ask the other coach.

Varsity, easy.

"Coach, these three numbers are illegal and if one or all play, it will cost you a technical foul."

blah blah blah

"Sorry, Coach, I can't be responsible for whether the officials in your previous games have enforced it."

blah blah blah

me walking away