This model Royal Singer was introduced in 1891, but they did not make it for a long period, I guess.
It is different from the earlier Singers, please look at my page about Singer safety development.
Down tube is more down, seat tube is curved and the saddle mount is transverse on the top tube.
I think (but I am not for sure, since I do not have the 1892-93 catalogues) that this model has been built for only one or two years. After that, there must have been an real Singer diamond frame.
But who has pictures of illustrations of that model?
The bicycle in the pictures was sold in 2012 by the Copake Auction in New York. It is not complete, but looks pretty original. Interesting is the steering lock, clearly different from the 'normal' version. But if you look closely to the illustration from the 1891 catalogue, you can see a white circle just under the top ball head bearing.
Is this the steering lock we see in the pictures?
I also have a page about this same model with pneumatic tires. Click link.