Two examples of the BF-109 'G model, one airworthy, one residing in the Smithsonian in DC. They made a bunch of these and they constitute a lot of surviving examples.
The 'greenhouse' framed cockpit was a good example of the Nazi regime's limited ability to produce complex perspex shapes at this stage. Everyone was using bubble canopies by this point of WW2.
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If you look at most German aircraft of the era, they feature extensive framing on the perspex cockpit pieces. Making large perspex bits with good optical quality is hard. It is a challenge for restorations nowadays because all the moulds and tooling are gone.
