Vintage BMW Motorcycle Owners

I apologize for the questions about my new to me R 50. But I’m trying to figure out what if anything the + 1 stamping on the upper left side of the engine case is. Thanks in advance for your expertise and time.
Also looking at buying complete exhaust system any pro or cons on chrome or SS. Thinking about buying the sports mufflers instead of the stock one mainly because of price. What’s the deal with a seemed or seem less is originality or appearance?
Any tips on sellers with discounts for single large purchases? Thanks everyone
I’ve tried using the search feature with not much success.

Sorry here’s the picture

The number was put there by the factory when assembled. It represents the variation in distance between centers of the camshaft and crankshaft in hundredths of millimeters. A positive number means that it was larger than standard. This helps identify what gear sets are used when assembling the engine. A bit of earlier discussion:

viewtopic.php?f=7&t=17393

Thanks guys for the links interesting read I will be listening for any noise from the cam gears while engine is running.
I haven’t had my bike fired up yet been checking everything over. It’s been setting for some 30 years so I’m changing all fluids and some seals,boots, and exhaust.