Identifying Jacobsen engine

Hi folks,
I'm stumped. I have several circa 1980s Jacobsen and Homelite self-propelled mowers with 3.5 and 5.0hp Briggs Quantum engines. Now, the various mowers differ slightly with baggers, turbo vacs, dead man switches, etc but the main engines are mostly the same. Without a model and serial number it's difficult ordering the correct parts. Briggs and Stratton says the numbers are stamped into the metal or sheetmetal in one of three locations on the mower. I've stripped one and can't see ANY number on the engine. A few have Jacobsen to Homelite (UT30084A) stickers on the deck but that isn't helping with engine ID. B+S insists it's there, but it's not for me to see? and I have looked at most of the 8. The carbs are Walbro with a Briggs logo cast into it but no numbers, either.
Do any of you have some concrete information or links about the Quantum 3.5 and 5hp? to get me closer.
Thanks from Nova Scotia
Chris

The numbers are there. Usually, very little to no disassembly is needed to locate them.

Can you supply pics of said engines?

The 3.5 HP will be on the air shroud/cover above the spark plug.... You might have to clean the area off with cleaner and soft brush Brass tooth brush style works well.....

Is the 5 HP the same style as the 3.5 ???? If so it's in the same place...

Let us know Mon Ami ~!~!

Sorry for the delay. I spent yesterday with a chipper issue. It's sunny this morning and I will look once again and post pics of one of the mowers. The 5hp and the 3.5 are both Quantum and look almost identical except that the various models have different linkages. Should have pics up by end of day!
Thanks
Chris

Success! I hauled out of hibernation and was cleaning up the 5hp Homelite readying it for the season and found the ID plate easily but the Jacobsens were my concern as I have 6 of them, and the ser.#/mod location was still a mystery until I started working on one, getting ready for Seafoam. I removed the air filter and there it was, stamped into the air filter backing plate that the cover mounts to! I've only replaced dozens of filters and assumed it was a part number for the plate! Kind of embarrassing as I had myself convinced there was none...Thanks for the help guys!:smile::smile::smile: Here are the two I talked about here. More to come as I gradually get to them. I've never assembled them all for a group shot but plan to. I've got mostly 3.5hp Jakes and a few Homelites 3.5 and 5hp. The 3.5 Quantum non-bagging Jacobsens are my very light and my favourites. The Homelite 5hp in the photo is noticeably heavier but a BEAST in the rough. It easily out does the 6 year old 6hp Honda self-propelled. It was so long and heavy with a rusting steel deck ( that I religiously cleaned after every use and stored inside) that I gave away. All my mowers are self-propelled and I've never had to do anything to the drivetrains or belts. Thanks again for you help.