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The following can be read in almost any Rowland manual:

The entire chassis is finely constructed from pieces of solid aluminum, each cut to a specific depth and thickness that, when bolted together, prevents any unwanted vibrations or resonances from reaching the audio signal within the unit. The entire chassis is also used as a heat sink to allow the unit to cool itself as efficiently as possible when necessary. The surface of the faceplate and top cover are carefully cut in a unique process that uses a diamond tipped blade. This process was refined over many years to produce an artistic and attractive finish which has been copied a number of times but never equaled. The faceplate is then finished with fine automobile polyurethane clear coat to preserve the clarity of the finish and allow the brilliant radiance of the diamond cut process to shine.

The manual also makes mention of being careful not to use any abrasive cleaning agents on the front surface. But if you're anything like me, you'll probably just glance over that section. And even if you've read it, again, if you're anything like me, you'll think you know better and go ahead anyway. A word of advice, and let me be absolutely clear about this:

DON'T USE PAINT THINNER ON YOUR FRONTPANEL!

If you do, you will remove (part of) the laquer that makes for the nice smooth finish. On the spot you touched, the aluminium will be darker and less shiny which is pretty visible under some lighting circumstances. A friend of mine learned this the hard way. He wanted to lift the power switch from the front panel of his model six, in order to replace the lamp. Following instructions of the distributor, he used adhesive tape. It worked fine but the tape had left some marks on the front panel which he removed by means of... you guessed it: paint thinner.