Help Identify 19?? CAT D7

Hi guys. I'm a newbie on this website. Our family has an old D7 that hasn't operated in 20+ years I'm guessing. It's been inside a shop it's whole life, but I cannot remember the last time it was used. The serial number is 3T8424SP. Can anyone tell me what year it is? My dad used to tell me it was from the '40s. I know it's a 3T series and very old. What does the SP at the end stand for? I've searched the internet for serial number info, but haven't found much. It has a gas pony...

Help Identify 19?? CAT D7

Help Identify 19?? CAT D7